Update README.md

As per the discussion here https://github.com/jejacks0n/mercury/issues/304
Fixed inserting Snippet in Chrome bug (issue #362)
Allow users to set a wrapperClass option on a snippet for additional wrapper element classes
Merge pull request #374 from jayzes/snippet-wrapper-class

Allow users to set a wrapperClass option on a snippet for additional wrapper element classes
Merge pull request #363 from sarink/master

Fixed inserting Snippet in Chrome bug (issue #362)
Merge pull request #306 from jasonwilliams200OK/patch-1

IE10 :: Update README.md