change keywords to be symbols and not words

this ensures that symbols like group_concat does not get matched and
font-locked with the keyword-face.

Closes #20.
fix font-locking where there are more then 1 # on a line

Previously, if there where more then 1 # on a line we would
only fontlock from the last #. Now it fontlocks from the first.
fix font-locking of comments and strings

the # character in strings is now font-locked with the string
instead of making the rest of the line a comment.

keywords and variable-names are now font-locked as
strings inside strings.

strings are font-locked with comment-face when inside
a comment.
remove unneeded save-excursion

since don't move, but just look at the character at current
point we don't need to save-excursion.