Envy

**e260da7**: add `clean --all` feature

**a2c47aa**: explicitly require 'mock' in tests_require in setup.py

**a083560**: Fix finding deeply nested files in a package. The following usage now works:

(some_env)$ envy edit package/subfolder/some_module.py

**06c4392**: Address problems with `vim` discussed in 4

If vim is set as $EDITOR, envy will use the standard default editor (vi) instead.

**a76b994**: alert user if they run envy with existing backup copy