Only auto-load .cson and .json keymap files

This now prevents files such as .DS_Store from being loaded as a
keymap where previously all paths were loaded regardless of extension.

Closes #205

src/app/atom-package.coffee

@@ -26,15 +26,12 @@ class AtomPackage extends Package
       @metadata = fs.readObject(metadataPath)
 
   loadKeymaps: ->
-    for keymapPath in @getKeymapPaths()
-      keymap.load(keymapPath)
-
-  getKeymapPaths: ->
     if keymaps = @metadata?.keymaps
-      keymaps.map (relativePath) =>
+      keymaps = keymaps.map (relativePath) =>
         fs.resolve(@keymapsDirPath, relativePath, ['cson', 'json', ''])
+      keymap.load(keymapPath) for keymapPath in keymaps
     else
-      fs.list(@keymapsDirPath)
+      keymap.loadDirectory(@keymapsDirPath)
 
   loadStylesheets: ->
     for stylesheetPath in @getStylesheetPaths()

src/app/keymap.coffee

@@ -35,7 +35,7 @@ class Keymap
     @loadDirectory(fs.join(config.configDirPath, 'keymaps'))
 
   loadDirectory: (directoryPath) ->
-    @load(filePath) for filePath in fs.list(directoryPath)
+    @load(filePath) for filePath in fs.list(directoryPath, ['.cson', '.json'])
 
   load: (path) ->
     @add(fs.readObject(path))