Revert "Remove the needless br-tags which are created on paste operations"

This reverts commit ed0c487d2684af1eb6e77b7fd24e8e614e2ee99b.
Revert "Remove node replacement with their sanitized children to preserve the tree structure"

This reverts commit b5dfadf1c4c699b52f09a470387d6b3e4c4fe787.
fix #1: preserve line breaks in pasted content
public grunt server for IE vm testing
remove html error in dummy.html