Use HTTPS instead of HTTP in build.py

https://groups.google.com/forum/#!topic/blockly/EDxPuJQ37RI

Closure compiler no longer accepts HTTP requests, as of last Thursday.  It is now HTTPS only.

Author: rachel-fenichel

blockly/build.py

@@ -270,7 +270,7 @@ def gen_generator(self, language):
   def do_compile(self, params, target_filename, filenames, remove):
     # Send the request to Google.
     headers = {"Content-type": "application/x-www-form-urlencoded"}
-    conn = httplib.HTTPConnection("closure-compiler.appspot.com")
+    conn = httplib.HTTPSConnection("closure-compiler.appspot.com")
     conn.request("POST", "/compile", urllib.urlencode(params), headers)
     response = conn.getresponse()
     json_str = response.read()