Fix highlighting when there are only 2 segments in theme

Here are two fixes:
- defaultdict makes it not throw KeyErrors.
- Replacing (False, False) with False makes it not throw vim.error (no color
  ctermbg=False)

powerline/renderers/terminal.py

@@ -26,12 +26,12 @@ class TerminalRenderer(Renderer):
 		'''
 		ansi = []
 		if fg is not None:
-			if fg[0] is False:
+			if fg is False or fg[0] is False:
 				ansi += [39]
 			else:
 				ansi += [38, 5, fg[0]]
 		if bg is not None:
-			if bg[0] is False:
+			if bg is False or bg[0] is False:
 				ansi += [49]
 			else:
 				ansi += [48, 5, bg[0]]

powerline/renderers/tmux.py

@@ -12,12 +12,12 @@ class TmuxRenderer(Renderer):
 			return ''
 		tmux_attr = []
 		if fg is not None:
-			if fg[0] is False:
+			if fg is False or fg[0] is False:
 				tmux_attr += ['fg=default']
 			else:
 				tmux_attr += ['fg=colour' + str(fg[0])]
 		if bg is not None:
-			if bg[0] is False:
+			if bg is False or bg[0] is False:
 				tmux_attr += ['bg=default']
 			else:
 				tmux_attr += ['bg=colour' + str(bg[0])]

powerline/theme.py

@@ -2,6 +2,7 @@
 
 import copy
 
+from collections import defaultdict
 
 class Theme(object):
 	def __init__(self, ext, colorscheme, theme_config, common_config, get_segment):
@@ -10,7 +11,7 @@ class Theme(object):
 		self.segments = []
 		self.EMPTY_SEGMENT = {
 			'contents': None,
-			'highlight': {self.colorscheme.DEFAULT_MODE_KEY: {'fg': (False, False), 'bg': (False, False), 'attr': 0}}
+			'highlight': defaultdict(lambda : {'fg': False, 'bg': False, 'attr': 0})
 			}
 		for side in ['left', 'right']:
 			self.segments.extend((get_segment(segment, side) for segment in theme_config['segments'].get(side, [])))