[sass mode] Improve indentation

Fixes bug #2156 for the most part

indention was bugged because it was reaching a wrong state when
any text that was not in the known set of words or patterns was
incurred.

for eg:
	head
		| <---- cursor should be here

and lets take  color : red as another example
now 'red' is same to the current tokenizer as 'head' from the first
example. So it indents for red automatically.

It was fixed by not letting any text after colon to reach the state
where it appends an indent after it.