Properly escape color codes in bash

Closes #177.
Closes #179.

powerline/bindings/bash/powerline.sh

@@ -12,8 +12,16 @@ _powerline_tmux_set_columns() {
 	_powerline_tmux_setenv COLUMNS "$COLUMNS"
 }
 
-trap "_powerline_tmux_set_columns" SIGWINCH
-kill -SIGWINCH "$$"
+_powerline_prompt() {
+	[[ -z "$POWERLINE_OLD_PROMPT_COMMAND" ]] ||
+		eval $POWERLINE_OLD_PROMPT_COMMAND
+	PS1="$(powerline shell left -r bash_prompt --last_exit_code=$?)"
+	_powerline_tmux_set_pwd
+}
 
-export PROMPT_COMMAND="_powerline_tmux_set_pwd"
-export PS1='$(powerline shell left --last_exit_code=$?)'
+trap "_powerline_tmux_set_columns" SIGWINCH
+_powerline_tmux_set_columns
+
+[[ "$PROMPT_COMMAND" == "_powerline_prompt" ]] ||
+	POWERLINE_OLD_PROMPT_COMMAND="$PROMPT_COMMAND"
+export PROMPT_COMMAND="_powerline_prompt"

powerline/renderers/bash_prompt.py

@@ -0,0 +1,18 @@
+# -*- coding: utf-8 -*-
+
+from powerline.renderers.shell import ShellRenderer
+
+
+class BashPromptRenderer(ShellRenderer):
+	'''Powerline bash prompt segment renderer.'''
+	def hl(self, contents=None, fg=None, bg=None, attr=None):
+		'''Highlight a segment.
+
+		Returns the default ShellRenderer escape sequence with \[...\] wrapped
+		around it (required in bash prompts).
+		'''
+		return '\[' + super(BashPromptRenderer, self).hl(None, fg, bg, attr) + '\]' + (contents or u'')
+
+	@staticmethod
+	def escape(string):
+		return string.replace('\\', '\\\\').replace('$', '\\$').replace('`', '\\`')