Fix SIMPLETAG/SIMPLEATTR fast path.

This regression (caused by 400b989d96d3d0b11482808ab0cccbda98ee3e98)
caused some quoted attributes containing a space then an ampersand or
\r to be incorrectly parsed.  (Malformed) tags with a \r or \n immediately
after a < were also being incorrectly parsed.

Added test case to exercise this code path.

Closes #45.