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.
Shoichi Aizawa
b64c445b61