DRY up checking if path is .cson or .json

src/app/text-mate-grammar.coffee

@@ -9,8 +9,7 @@ module.exports =
 class TextMateGrammar
   @readFromPath: (path) ->
     grammarContent = null
-    extension = fs.extension(path)
-    if extension is '.cson' or extension is '.json'
+    if fs.isObjectPath(path)
       grammarContent = fs.readObject(path)
     else
       plist.parseString fs.read(path), (e, data) ->

src/packages/snippets/lib/load-snippets-handler.coffee

@@ -20,9 +20,7 @@ module.exports =
 
       continue if fs.base(snippetsPath).indexOf('.') is 0
       try
-        extension = fs.extension(snippetsPath)
-        objectExtension = extension is '.cson' or extension is '.json'
-        if objectExtension and object = fs.readObject(snippetsPath)
+        if fs.isObjectPath(snippetsPath) and object = fs.readObject(snippetsPath)
           snippets.push(object)
         else if object = fs.readPlist(snippetsPath)
           snippets.push(object)

src/stdlib/fs.coffee

@@ -186,6 +186,10 @@ module.exports =
     base = @base(path, extension).toLowerCase()
     base is 'readme' and (extension is '' or @isMarkdownExtension(extension))
 
+  isObjectPath: (path) ->
+    extension = @extension(path)
+    extension is '.cson' or extension is '.json'
+
   readObject: (path) ->
     contents = @read(path)
     if @extension(path) is '.cson'