Support the first-non-tab and until-last-tab match modes.

Tag matching (CtrlPTag) requires first-non-tab support to work as
expected--matching against the tag only, instead of including the path.
The until-last-tab mechanism is used by CtrlPChange.

This also fixes #4.
Merge pull request #10 from jszakmeister/support-other-match-modes

Support the first-non-tab and until-last-tab match modes.