Anaconda has packages that override at least sed
Greadlink is also a critical executable if present

Closes #1459

infocmp is a system utility that returns information about the user's terminal. When it is shimmed it can cause problems for various programs that use it to determine terminal settings. In particular, the library used by the Scala shell reads it and problems can occur where various control keys don't work (e.g. backspace does not work).

Add `clear` to the Anaconda's default blacklist in order to prevent
pyenv from creating the shim script for it.

The `clear` command executable began included from Anaconda 5.0.0
onwards, and this executable now conceals that of the user's base system
- this hinders the user from running the `clear` command with the
`command not found` error output if a user installs and selects one or
more Python version(s) other than Anaconda 5.x.x.

Adding this one-liner to the blacklist allows the user to use the
`clear` command even when Anaconda 5.x.x is not selected by pyenv.

Add `tput` to the Anaconda's default blacklist in order to prevent pyenv
from creating the shim script for it.

Anaconda 5.0.0 contains some executables which are part of the base
system. Many of these executables did not exist in the last major
version of Anaconda (`4.4.0`), and the existence of pyenv's shim
scripts for these executables in `5.0.0` can cause to conceal those
executables in the user's base system; for the details, please see the
discussion with @yyuu at #992.

This commit resolves a coloured output error when running a terminal
command which uses `tput`. This error occurs when multiple Python
versions are installed alongside `anaconda2-5.0.0` or `anaconda3-5.0.0`
and neither of those two Anaconda versions is selected by pyenv.