Revert "Remove podspec for EmojiKeyboard as replaced by AGEmojiKeyboard"

This reverts commit c1b526d4b0a7deea50e55c8eabbbfc753eb7f3e3.
Add depracation declaration to EmojiKeyboard podspec

Deprecated in favor of 'AGEmojiKeyboard' (https://github.com/ayushgoel/AGEmojiKeyboard).