Track latest version of purescript-timers

They aren't tagging releases so when their API shifts, you end up
getting the latest. They changed their namespace. Note that you should
also merge a similar PR I made for purescript-test-unit, as that may
obstruct the building of this library.
Merge pull request #17 from MichaelXavier/purescript-timers-update

Track latest version of purescript-timers