expose match spans via new method

[matanox]

Enables #63.
Obviously this is too opinionated, so I doubt you'll merge this. But it is helpful to have this added control, as the original implementation seems to conceal retrieving the spans.

I've no idea why my editor added the superfluous white-space differences in the diff, but these can be easily undone if this gets a green light to merge.

Basically I've added a method getAllGroupSpans exposing the java.util.regex object holding the spans.

[coveralls]

Coverage increased (+0.02%) to 99.359% when pulling 32d0b63 on matanster:master into f311b15 on VerbalExpressions:master.