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.
