Bash example had a missing quote for setting PYENV_ROOT path

Describe more clearly for different shells.

This PR fixes (currently harmless) warning on macOS when homebrew is *not* installed.

- [ ] Test case (required?)

For example:

```sh
wadkar$ pyenv install 3.8.2
/Users/wadkar/.pyenv/plugins/python-build/bin/python-build: line 1541: brew: command not found
/Users/wadkar/.pyenv/plugins/python-build/bin/python-build: line 1541: brew: command not found
Installing openssl-1.1.0j...
Installed openssl-1.1.0j to /Users/wadkar/.pyenv/versions/3.8.2

Installing readline-8.0...
Installed readline-8.0 to /Users/wadkar/.pyenv/versions/3.8.2

Installing Python-3.8.2...
python-build: use zlib from xcode sdk
Installed Python-3.8.2 to /Users/wadkar/.pyenv/versions/3.8.2
```

Update the bats link to https://github.com/bats-core/bats-core (which is what pyenv is actually using on [Travis](https://github.com/pyenv/pyenv/blob/master/.travis.yml#L35))

https://www.openssl.org/source/openssl-1.0.2*
  => https://www.openssl.org/source/old/1.0.2/openssl-1.0.2*

https://www.openssl.org/source/openssl-1.1.0*
  => https://www.openssl.org/source/old/1.1.0/openssl-1.1.0*

Co-authored-by: Sean Gies <seangies@apple.com>

* Update help docs to clarify multiple version(s) are allowed

* Tweek version(s) help description

Fixes #623

Update miniconda builds

README, better docs + logging

Scrapes available miniconda builds from anaconda repo

I skimmed past the requires post-installation steps for Homebrew when walking though the README. 
Anecdotally, other devs noted the same issue.

The pyenv help listing offered the "commands" command twice.

https://docs.travis-ci.com/user/reference/osx/#macos-version

https://github.com/pyenv/pyenv/issues/1400#issuecomment-551371058

Closes #846, #1400, #1447, #1449

Add PyPy 7.3.0

The official pypy builds should now be portable on linux.
Also add aarch64 builds.

Fix simple typo: abovementioned -> above

Closes #1485

Grammatical corrections

Closes #1459

```
checksum mismatch: Python-3.5.8.tar.xz (file is corrupt)
expected 1bb1319bcd05d95c4d9752c7f6378c5378b8f467fb9045e07023e94b28b2ff41, got 55a345c78ee3afbc2e60678442aad7bcc384ddea5bb95f8d66edc4868d4847d4
```

Add CPython 2.7.17

## before
```Usage: pyenv <command> [<args>]

Some useful pyenv commands are:
   commands    List all available pyenv commands
   local       Set or show the local application-specific Python version
   global      Set or show the global Python version
   shell       Set or show the shell-specific Python version
   install     Install a Python version using python-build
   uninstall   Uninstall a specific Python version
   rehash      Rehash pyenv shims (run this after installing executables)
   version     Show the current Python version and its origin
   versions    List all Python versions available to pyenv
   which       Display the full path to an executable
   whence      List all Python versions that contain the given executable

See `pyenv help <command>' for information on a specific command.
For full documentation, see: https://github.com/pyenv/pyenv#readme
```

## after
```
Usage: pyenv <command> [<args>]

Some useful pyenv commands are:
   commands    List all available pyenv commands
   local       Set or show the local application-specific Python version
   --version   Display the version of pyenv
   commands    List all available pyenv commands
   exec        Run an executable with the selected Python version
   global      Set or show the global Python version
   help        Display help for a command
   hooks       List hook scripts for a given pyenv command
   init        Configure the shell environment for pyenv
   install     Install a Python version using python-build
   local       Set or show the local application-specific Python version
   prefix      Display prefix for a Python version
   rehash      Rehash pyenv shims (run this after installing executables)
   root        Display the root directory where versions and shims are kept
   shell       Set or show the shell-specific Python version
   shims       List existing pyenv shims
   uninstall   Uninstall a specific Python version
   update      update pyenv and plugins
   version     Show the current Python version and its origin
   version-file   Detect the file that sets the current pyenv version
   version-name   Show the current Python version
   version-origin   Explain how the current Python version is set
   versions    List all Python versions available to pyenv
   whence      List all Python versions that contain the given executable
   which       Display the full path to an executable

See `pyenv help <command>' for information on a specific command.
For full documentation, see: https://github.com/pyenv/pyenv#readme
```