feat(build runner): added in context, dockerfile_location

this is a new feature meant to allow people to use any file as
  a dockerfile and any folder as a context directory

buildtrigger/githubhandler.py

@@ -371,17 +371,22 @@ class GithubBuildTrigger(BuildTriggerHandler):
       raise RepositoryReadException(message)
 
     path = self.get_dockerfile_path()
-    if not path or not self.filename_is_dockerfile(os.path.basename(path)):
+    if not path:
       return None
 
     try:
       file_info = repo.get_file_contents(path)
-    except GithubException as ghe:
+    # TypeError is needed because directory inputs cause a TypeError
+    except (GithubException, TypeError) as ghe:
+      logger.error("got error from trying to find github file %s" % ghe)
       return None
 
     if file_info is None:
       return None
 
+    if isinstance(file_info, list):
+      return None
+
     content = file_info.content
     if file_info.encoding == 'base64':
       content = base64.b64decode(content)