Added "caseSensitive" parameter 

Currently before accepting new entries on the input there's a check that checks whether this tag is already present. This check is case insensitive. 
Though, there are occasions where capital letters matter. For this reason I added a new (boolean) parameter called "caseSensitive". This parameter is by default "false" (that means the input checks tags existence in a case-insensitive manner, exactly as it is now). 
If the user wants to make the check case-sensitive then he can enter this parameter with value "true" on the tag.
Example: 
-- without case-sensitive
Having entered the "abc" tag in the input "Abc" is not acceptable
-- with case-sensitive="true"
Having entered the "abc" tag in the input "Abc" is also accaptable