Filter out Github user invalid-email-address from contributors.
Filter out Github user invalid-email-address from contributors.

Fixes Issue 17: https://github.com/open-city/civic-json-worker/issues/17

MaxPresman/cfapi,smalley/cfapi,0111001101111010/cfapi,smalley/cfapi,EvanHahn/civic-json-worker,codeforamerica/cfapi,EvanHahn/civic-json-worker,MaxPresman/cfapi,0111001101111010/cfapi,smalley/cfapi,codeforamerica/cfapi,MaxPresman/cfapi,chihacknight/civic-json-worker,open-city/civic-json-worker