Add color plugin

[hoelzro]

Something similar to pry's/bpython's/fish's coloration would be cool, for both entered code and things like stack traces.

[mmcdaris]

+1

[henry4k]

I just tried to write such a plugin for your REPL, but neither lua-repl nor linenoise
provide access to single modification events. Seems that linenoise must either be
patched or that a completly different input library is needed.

[hoelzro]

@henry4k Thanks for pointing that out; that's definitely something that needs to be done in other for this plugin to work.