support for TypeScript dependencies

wakatime/dependencies/__init__.py

@@ -123,8 +123,6 @@ class DependencyParser(object):
 
     @property
     def root_lexer(self):
-        if not self.lexer:
-            return None
         if hasattr(self.lexer, 'root_lexer'):
             return self.lexer.root_lexer
         return self.lexer

wakatime/dependencies/javascript.py

@@ -54,3 +54,7 @@ class JavascriptParser(TokenParser):
         content = content.split('/')[-1].split('\\')[-1]
         content = self.extension.sub('', content, count=1)
         return content
+
+
+class TypeScriptParser(JavascriptParser):
+    pass