Alter plugin layout: move *.plugin to *.{ext}.plugin

I do not see why vim plugins should receive such a generic name as
`powerline.segments.plugin.gundo`: taking a name that clearly indicates that
`gundo` is a *vim* plugin is better.

powerline/config_files/config.json

@@ -34,10 +34,10 @@
 				"help": "help",
 				"quickfix": "quickfix",
 
-				"powerline.matchers.plugin.nerdtree.nerdtree": "plugin_nerdtree",
-				"powerline.matchers.plugin.ctrlp.ctrlp": "plugin_ctrlp",
-				"powerline.matchers.plugin.gundo.gundo": "plugin_gundo",
-				"powerline.matchers.plugin.gundo.gundo_preview": "plugin_gundo-preview"
+				"powerline.matchers.vim.plugin.nerdtree.nerdtree": "plugin_nerdtree",
+				"powerline.matchers.vim.plugin.ctrlp.ctrlp": "plugin_ctrlp",
+				"powerline.matchers.vim.plugin.gundo.gundo": "plugin_gundo",
+				"powerline.matchers.vim.plugin.gundo.gundo_preview": "plugin_gundo-preview"
 			}
 		},
 		"wm": {

powerline/config_files/themes/vim/default.json

@@ -55,13 +55,13 @@
 			},
 			{
 				"exclude_modes": ["nc"],
-				"module": "powerline.segments.plugin.syntastic",
+				"module": "powerline.segments.vim.plugin.syntastic",
 				"name": "syntastic",
 				"priority": 50
 			},
 			{
 				"exclude_modes": ["nc"],
-				"module": "powerline.segments.plugin.tagbar",
+				"module": "powerline.segments.vim.plugin.tagbar",
 				"name": "current_tag",
 				"draw_soft_divider": false,
 				"priority": 50

powerline/config_files/themes/vim/plugin_ctrlp.json

@@ -1,5 +1,5 @@
 {
-	"default_module": "powerline.segments.plugin.ctrlp",
+	"default_module": "powerline.segments.vim.plugin.ctrlp",
 	"segments": {
 		"left": [
 			{

powerline/config_files/themes/vim/plugin_nerdtree.json

@@ -1,5 +1,5 @@
 {
-	"default_module": "powerline.segments.plugin.nerdtree",
+	"default_module": "powerline.segments.vim.plugin.nerdtree",
 	"segments": {
 		"left": [
 			{

powerline/matcher.py

@@ -13,7 +13,7 @@ def gen_matcher_getter(ext, import_paths):
 		oldpath = sys.path
 		sys.path = import_paths + sys.path
 		try:
-			return getattr(__import__(match_module, fromlist=[match_function]), match_function)
+			return getattr(__import__(str(match_module), fromlist=[str(match_function)]), match_function)
 		finally:
 			sys.path = oldpath
 	return get

powerline/segment.py

@@ -58,8 +58,9 @@ def get_function(data, segment):
 	oldpath = sys.path
 	sys.path = data['path'] + sys.path
 	segment_module = str(segment.get('module', data['default_module']))
+	name = str(segment['name'])
 	try:
-		return None, getattr(__import__(segment_module, fromlist=[segment['name']]), segment['name']), segment_module
+		return None, getattr(__import__(segment_module, fromlist=[name]), name), segment_module
 	finally:
 		sys.path = oldpath