Remove filename from inspect method signature #109

The abstract method inspect of the inspector class has a filename as an argument. This isn't actually used in the call; it should only take the single argument of the kwargs dictionary. This is largely cosmetic, as long as any classes that override the method use the right signature, but it could be confusing.

OS, Python version, and dependency version information:

Linux-4.15.0-163-generic-x86_64-with-Ubuntu-18.04-bionic
sys.version_info(major=2, minor=7, micro=17, releaselevel='final', serial=0)
sqlalchemy=1.1.11

Version of dbprocessing

Current master

Closure condition

First need to verify that there are no implications of removing this, then merge a PR which removes any references to it in the documentation, and removes the filename from the signature. This probably isn't a big one, but I don't have time right now to do the digging and verification.