Added some asserts

Code analysis was warning me of the potential null situation. I'm pretty
sure these things can never actually be null, but doesn't hurt to have
an assert just in case. After all, that's what they're there for. :)
Removed unused lastFlushTime

This field was being assigned, but never actually read.
Ensure GetExecutingAssembly called at right time

My last change caused this method to be called in cases where it could
potentially throw an exception.
Merge pull request #23 from github/haack-fixups

Haack fixups