fix(buildtrigger): fixed error from github api

there was a 500 being thrown every time there was a slash at the end of a directory while adding in a new trigger this stops that 500 from coming

buildtrigger/basehandler.py

@@ -259,7 +259,7 @@ class BuildTriggerHandler(object):
     pass
 
   @classmethod
-  def path_is_dockerfile(cls, file_name):
+  def filename_is_dockerfile(cls, file_name):
     """ Returns whether the file is named Dockerfile or follows the convention <name>.Dockerfile"""
     return file_name.endswith(".Dockerfile") or u"Dockerfile" == file_name