Update README.mdown

Properly hides the HUD at completion.
MBLabelAlignmentCenter doesn't need to be in header, could end up with multi-declaration of value
Merge pull request #112 from coryallegory/master

MBLabelAlignmentCenter risk of being defined multiple times
Merge pull request #109 from dnstevenson/master

Fixed example in Readme
README cleanup and cocoapods instructions.