Prevent invalid byte sequence errors when invoking 'brew info'

'brew info' would show a unicode character for dependencies to indicate
wether they're met or not. Setting the HOMEBREW_NO_EMOJI var prevents this:
https://github.com/Homebrew/homebrew/commit/9b173745e4341200721c6200a583d66c8c2b1433
Merge pull request #2 from jasperla/utf8

Prevent invalid byte sequence errors when invoking 'brew info'