markdown error: header was not rendered due to extraneous spacing
markdown error: header was not rendered due to extraneous spacing

Summary:
markdown header not rendered correctly. before:

![image](https://cloud.githubusercontent.com/assets/51902/14881360/e6082d70-0d33-11e6-99de-051d21d77632.png)

after:

![image](https://cloud.githubusercontent.com/assets/51902/14881369/f1cd7d36-0d33-11e6-9e92-7388c9713b62.png)
Closes https://github.com/facebook/flow/pull/1724

Differential Revision: D3236272

Pulled By: mroch

fb-gh-sync-id: 37f557173bac335ed947f980d26c88f34fb8f793
fbshipit-source-id: 37f557173bac335ed947f980d26c88f34fb8f793

JonathanUsername/flow,samwgoldman/flow,jgrund/flow,gabro/flow,samwgoldman/flow,jeffmo/flow,chenglou/flow,mroch/flow,AprilArcus/flow,facebook/flow,popham/flow,jgrund/flow,ylu1317/flow,mroch/flow,nmote/flow,samwgoldman/flow,jamesgpearce/flow,nmote/flow,nmote/flow,cesarandreu/flow,AgentME/flow,facebook/flow,MichaelDeBoey/flow,jamesgpearce/flow,mroch/flow,jdelStrother/flow,mroch/flow,jamesgpearce/flow,jamesgpearce/flow,mroch/flow,popham/flow,nmote/flow,ylu1317/flow,samwgoldman/flow,mroch/flow,fletcherw/flow,facebook/flow,TiddoLangerak/flow,gabro/flow,AgentME/flow,AprilArcus/flow,ForbesLindesay/flow,AprilArcus/flow,AgentME/flow,samwgoldman/flow,MichaelDeBoey/flow,nmote/flow,popham/flow,ylu1317/flow,claudiopro/flow,jeffmo/flow,jamesgpearce/flow,facebook/flow,nmote/flow,fletcherw/flow,gabelevi/flow,MichaelDeBoey/flow,ForbesLindesay/flow,jeffmo/flow,AprilArcus/flow,claudiopro/flow,claudiopro/flow,popham/flow,claudiopro/flow,JonathanUsername/flow,chenglou/flow,gabro/flow,ylu1317/flow,nmote/flow,cesarandreu/flow,gabro/flow,fletcherw/flow,jdelStrother/flow,AgentME/flow,popham/flow,gabro/flow,claudiopro/flow,JonathanUsername/flow,JonathanUsername/flow,MichaelDeBoey/flow,jdelStrother/flow,jamesgpearce/flow,mroch/flow,AprilArcus/flow,jgrund/flow,AgentME/flow,popham/flow,gabelevi/flow,JonathanUsername/flow,jgrund/flow,jamesgpearce/flow,jdelStrother/flow,JonathanUsername/flow,JonathanUsername/flow,chenglou/flow,ForbesLindesay/flow,gabro/flow,cesarandreu/flow,ForbesLindesay/flow,fletcherw/flow,TiddoLangerak/flow,facebook/flow,AprilArcus/flow,ForbesLindesay/flow,jeffmo/flow,gabelevi/flow,jgrund/flow,fletcherw/flow,gabelevi/flow,gabelevi/flow,MichaelDeBoey/flow,jdelStrother/flow,gabelevi/flow,TiddoLangerak/flow,chenglou/flow,facebook/flow,chenglou/flow,cesarandreu/flow,ylu1317/flow,TiddoLangerak/flow,jeffmo/flow,chenglou/flow,samwgoldman/flow,jgrund/flow,facebook/flow,TiddoLangerak/flow,popham/flow,samwgoldman/flow,fletcherw/flow,jdelStrother/flow,ForbesLindesay/flow,jeffmo/flow,gabelevi/flow