Only call `bold()` on 'release_name' if value is not None

Sometimes the API returns a None in the 'release_name' field, which
causes issues with the `''.join()` function used in `bold()`.
Use '\e[22m' to only reset emphasis and not colour after bold

'\e[0m' will reset all ANSI SGR attributes, but since we only set the
bold attribute '\e[22m' should be used instead just in case the user has
a custom colour set in their terminal.

Tested in xterm, urxvt, VTE, linux framebuffer console and OSX Terminal.
Update tests for new bold escape code '\e[22m'
Merge pull request #28 from quigybo/bold_fixes

Miscellaneous fixes for the new bold printing