Clear highlight groups on ColorScheme event

Closes #196
Fixes #153
Fixes #194

powerline/bindings/vim/plugin/powerline.vim

@@ -72,4 +72,5 @@ augroup Powerline
 	autocmd!
 	autocmd BufEnter,BufWinEnter,WinEnter,CmdwinEnter * call s:UpdateWindows(0) | redrawstatus
 	autocmd CmdwinLeave * call s:UpdateWindows(1)
+	autocmd ColorScheme * exec s:powerline_pycmd 'powerline.renderer.reset_highlight()'
 augroup END

powerline/renderers/vim.py

@@ -44,6 +44,9 @@ class VimRenderer(Renderer):
 		statusline = super(VimRenderer, self).render(mode, winwidth, theme, segments)
 		return statusline
 
+	def reset_highlight(self):
+		self.hl_groups.clear()
+
 	@staticmethod
 	def escape(string):
 		return string.replace('%', '%%')