Expose termcolor's ColorChoice and make colors optional

[mrkline]

• TermLogger: Expose termcolor::ColorChoice

  Command line interfaces that write colored output usually give users an option to turn it off, or make it automatically shut off when writing to a file, pipe, or unsupported terminal. termcolor already has some nice machinery to handle this sort of thing with ColorChoice, so expose it when creating a TermLogger.

  Programmers (such as myself) who use simplelog and want to give users this choice only have ugly alternatives. For example, you could fall back to a WriteLogger if the user doesn't want color, but then you:

  • Lose out on the "mixed" logging mode you get from TerminalMode::Mixed

  • Have to reimplement nice ColorChoice::Auto behavior yourself, on top of termcolor.

• TermLogger/ConfigBuilder: Make colors optional

  White isn't a good default for those with light terminal screens (brighter background, darker text). This is already trivial in termcolor, so just allow level colors to be None.

[coveralls]

Coverage increased (+0.7%) to 67.888% when pulling a17ca28ffad2e61cadfff27f85245509f99cfe95 on mrkline:optional-color into 8338b80979bcae391a8c5bc61f13e174bc118cb2 on Drakulix:master.

[Drakulix]

thx!