Changes to text and ascii color handling

[dylanaraps]

This PR changes the way we set text and ascii colors allowing us to
set the text to distro colors in any image mode.

By default text will be colored according to your distro's logo colors
no matter what image mode you're in. The current implementation
in master only works when the user is in ascii mode.

This PR removes all of the *_colors options and replaces them
with a single colors variable and flag. For example:

# Colors the text in this order:
# title, @, underline, subtitle, colon, info
# --colors 1 2 3 4 5 6
colors=(1 2 3 4 5 6)

# Colors the text according to distro logo.
# This is default
# --colors distro
colors=(distro)

Using --colors with no arguments will now disable text colors
entirely. (fetch --colors)

Another cool feature is that when $colors is set to distro and you
change --ascii_colors or $ascii_colors to a custom value the text
changes with it.

I'm still working on this but it's pretty much complete, let me know
what you guys think about it.