bump version to 1.7.5
Adding locker#assert to not fail loudly.

This is to close out request issue #48 on the Github repository. Basically return true
if we obtain the lock (and have a connection, etc.) otherwise return false and don't fail
loudly as locker#assert! does.
Merge pull request #62 from johnbellone/issue/48

Implemented locker#assert to not fail loudly.
Merge branch 'master' of github.com:slyphon/zk
simplify the non-bang assert method
prep for 1.8.0 release