fix infinite loop when change textview height for iOS6
Merge branch 'master' of https://github.com/Aevit/MessageDisplayKit

# By Jack
# Via Jack (2) and Aevit (1)
* 'master' of https://github.com/Aevit/MessageDisplayKit: (44 commits)
  Change the icon png files
  fix the KVO bug
  Add podspec support to v0.1.0
  fix load DataSource to main queue.
  fix iOS6 UI layout bug
  Fix more bug and add multi media message
  Update README.md
  Update README.md
  fix the textView show other menu.
  change code style.
  Change arrow Photo
  Add send photo message
  Category the message media type.
  Fix the iOS7 Gesture bug.
  Change demo DataSource.
  delete png file.
  fix the issue5
  fix the iOS7 bug, change label to textView.
  Configure the style of the cell
  Finish DataSource / Delegate IMP.
  ...