Add a minimal word count IO function
Add first SGML parser attempt

Lots of scratch code in this file currently. This is the first working
parser in this repo. Subsequent commits will involve cleaning up the
code and implementing larger cominbations of parsers.
Add SgmlLine type contructor
Change value parser and sgmlHead parser.

1) The value parser parsed input with Parsec.anychar, which consumed
the final '\n' character, making it impossible to parse the next line
iteratively. It was changed to use Parsec.noneOf.

2) sgmlHead finally works because of the previous change.