Switch to a new Twitter dev app

We killed the old one during #2239.
Fix GitHub dev app; #2239
Merge pull request #2276 from gittip/fix-dev-apps

fix dev apps
Merge pull request #2277 from gittip/fix-github-app

Fix GitHub dev app; #2239
Fix Bitbucket dev #2253
Merge pull request #2278 from gittip/fix-bitbucket-dev

Fix Bitbucket dev #2253