Add street address search

[mileswwatkins]

I noticed that it was on the to-do list, and thought it'd be a nice feature to include.

I took a guess as to how you might like to handle imprecise geocoding, but let me know if you'd like me to tweak that Exception or any other piece.

[mileswwatkins]

Hmm, looks like Travis hit a bunch of unrelated bugs in tests.test_image.TestProcess that didn't pop up for me locally.

[scisco]

Will reopen if the PR is updated to pass tests

[mileswwatkins]

The tests pass locally for me; I think the push CI test isn't passing because my PR's coming from an external (forked) repo instead of the main developmentseed repo.

[scisco]

Moving this to #125