Minor fixes after testing with some "noisy" data

Looks like a lot of changes, but really just a few:
1. Added some checks that input image files exist
2. Added an exception handler to the row process
3. Added the ability to use tag other than "vector" for these (I needed
to use tag "svg")
4. Added a few switches to turn off a few things I personally didn't
need (but kept the defaults as they were originally)
Merge pull request #2 from csmoore/master

Minor improvements after testing with some "noisy" data - Looks good, thanks for adding more robust handling for incomplete data