Fixed F_MEAS/T_MEAS bug

F_MEAS was not being reset to 0 following routes with only 1 itinerary
segment
Improved arterial matching
Keep memory clearer
Fixed path_errors.txt issue

SAS didn't know where to create it, and Python didn't look for it
anyway.
Add message ID'ing MHN path
Stop processing if itins begin/end with non-existent node

Existing nodefix macro logic cannot fix these. Python script would
subsequently fail when trying to build routes.
Merge pull request #52 from nmpeterson/master

More bug fixes, general improvements