Add viewabilityState to results.  This field should always contain "viewabile", "notViewable", or "unmeasurable".  A unit is "unmeasurable" if EI is unavailable, the unit cannot be found, the unit is in an iframe, or the viewport could not be determined.
Devs don't need to pass in a UID anymore, UID is now generated by the library.
Fixed .gitignore
Fixed syntax typo
merged from master
cleanup
fixed misspelling of discernible