Addd “default_module” theme key support

Refs #3.

docs/source/configuration.rst

@@ -133,6 +133,11 @@ Themes
 ``name``
     Name of the theme.
 
+``default_module``
+    .. _config-themes-default_module:
+
+    Python module where segments will be looked by default.
+
 ``segments``
     A dict with a ``left`` and a ``right`` list, consisting of segment 
     dicts. Each segment has the following options:
@@ -161,7 +166,8 @@ Themes
         .. _config-themes-seg-module:
 
         Function module, only required for function segments. Defaults to 
-        ``core``.
+        ``powerline.ext.{extension}.segments``. Default is overriden by 
+        :ref:`theme option <config-themes-default_module>`.
 
     ``name``
         .. _config-themes-seg-name:

powerline/core.py

@@ -30,7 +30,7 @@ class Powerline(object):
 		# Load and initialize extension theme
 		theme_config = self._load_theme_config(ext, self.config_ext.get('theme', 'default'))
 		path = [os.path.expanduser(path) for path in self.config.get('paths', [])]
-		get_segment = Segments(ext, path, colorscheme).get
+		get_segment = Segments(ext, path, colorscheme, theme_config.get('default_module')).get
 		self.get_matcher = Matchers(ext, path).get
 		theme_kwargs = {
 			'ext': ext,

powerline/segments.py

@@ -5,15 +5,15 @@ import sys
 
 
 class Segments(object):
-	def __init__(self, ext, path, colorscheme):
-		self.ext = ext
+	def __init__(self, ext, path, colorscheme, default_module=None):
+		self.default_module = default_module or 'powerline.ext.{0}.segments'.format(ext)
 		self.path = path
 		self.colorscheme = colorscheme
 
 	def get_function(self, segment):
 		oldpath = sys.path
 		sys.path = self.path + sys.path
-		segment_module = str(segment.get('module', 'powerline.ext.{0}.segments'.format(self.ext)))
+		segment_module = str(segment.get('module', self.default_module))
 		try:
 			return None, getattr(import_module(segment_module), segment['name']), '{0}.{1}'.format(segment_module, segment['name'])
 		finally: