Adding highlighting words

Added highlighting words:
Users may now use the new highlight commands:
-Use /highlight add, word to add a highlighting word.
You might add several words separated with commands.
-In a likewise fashion, /highlight delete, word deletes words.
-Using /highlight delete with no words will delete all.
-/highlight show or list will show all current highlight words.
-By default no word is added to highlights.
-Words are escaped
Merge pull request #5 from Joimer/patch-1

Adding highlighting words