Colorize logs for easier readability

[ZenithDK]

It would be nice to have some colors added to the mopidy log output to make it easier to spot errors, warnings, etc.

A quick search led me to this library: https://pypi.python.org/pypi/coloredlogs

I tested it out quickly by just inserting that snippet of code, and this was what I got:

[jodal]

This would be really nice.

Though, I'm more positive to colorama since it is packaged in Debian and also works on Windows.

[trygveaa]

I would prefer if the dependency is optional. Both because I like few dependencies in general, and since none of those are packaged in Arch.

[ZenithDK]

Nice, I like how we get colorized logs and yet do not get any new dependencies.
Thanks @jodal!

[jodal]

I found colorama to be quite optional, but very useful the second you require Windows support.

If we ever start supporting Windows seriously, we just need to add an optional dependency on colorama and if colorama is present run:

import colorama
colorama.init()

...and let the colorization code run on Windows as well, and it should work seamlessly there too.