feature/truecolor: TrueColor Theming Support

Adds the ability to use (R,G,B) tuples in theme files to more accurately
specify the colors desired for each segment.
Not all terminals have TrueColor support, so in the case that a theme
uses (R,G,B) tuples that cannot be supported by the current terminal,
the colors are approximated using colortrans.rgb2short to bring them to
the nearest xterm-256 color.

powerline_shell/__init__.py

@@ -6,6 +6,7 @@ import os
 import sys
 import importlib
 import json
+from . import colortrans
 from .utils import warn, py3, import_file
 import re
 
@@ -86,6 +87,10 @@ class Powerline(object):
     def __init__(self, args, config, theme):
         self.args = args
         self.config = config
+        theme_wants_truecolor = hasattr(theme, "use_truecolor") and theme.use_truecolor
+
+        env_colorterm = os.getenv("COLORTERM")
+        self.truecolor_supported = env_colorterm is not None and "truecolor" in env_colorterm
         self.theme = theme
         self.cwd = get_valid_cwd()
         mode = config.get("mode", "patched")
@@ -105,6 +110,12 @@ class Powerline(object):
             return ''
         elif code == self.theme.RESET:
             return self.reset
+        elif isinstance(code, tuple):
+            # Do we support TrueColor? If not, supply the closest possible xterm-256 color.
+            if self.truecolor_supported:
+                return self.color_template % ('[%s;2;%s;%s;%sm' % (prefix, *code))
+            else:
+                return self.color_template % ('[%s;5;%sm' % (prefix, colortrans.rgb2short(*code)))
         else:
             return self.color_template % ('[%s;5;%sm' % (prefix, code))