init: zsh: prepend hook to precmd_functions

This makes sure that $VIRTUAL_ENV is handled already in other precmd
functions, especially your prompt.

Passing return value from executed command.

find proper source version from pyenv if the given executable is only
basename or is a shim script.

pyenv-virtualenv-init fix for fish

update init step in brew installation instructions

This fixes issue: https://github.com/yyuu/pyenv-virtualenv/issues/36

Apply code blocks style

https://www.python.org/dev/peps/pep-0370/

Manage Anaconda/Miniconda environment as a pyenv version

an executable is not found in it, automatically look up the executable
for source Python version. (fixes #62)

init: fix shell detection when invoked from a script

- fixes `ps` command to lookup parent process
 - adds `assert_output_contains_not` test helper

Ref: https://github.com/yyuu/pyenv/issues/373

It will be done by `get-pip.py` and we don't have to do anything explicitly.

First release after my son's birth....

activate: do not display note if initialized already

Use `typeset -g` with `precmd_functions`

This fixes displaying the note, in case "init" has been run manually
and/or the init is not in the expected place.

It removes the unnecessary calls to "grep".

pyenv-virtualenv-init will look at `$PYENV_SHELL` now, too.

Tests have been adjusted/fixed.

Usage: version is optional

minor: fix comments