Add full color support

[jonhoo]

Currently, inferno's flamegraph implementation just hardcodes the color of all the frames in the flamegraph. That's makes the flamegraph significantly less useful, and also much less pretty. Instead, we should support flamegraph.pl's --colors option. It affects colors in a number of ways:

• The background color changes
• It colors individual frames through this serious function (which should live in its own module)
• Some of the color modes do extra funky color things like "chain"
• When combined with the --hash flag, the namehash coloring function is used, which attempts to color similar "parts" of the stack similarly, and consistently across runs.

We should support all that! It's probably most a matter of porting the giant color function.

[jonhoo]

Fixed in #32!