Fix #70 - Add summary text for predictions with same route/headsign

[barbeau]

• Uses new utility method in the onebusaway-client-library, implemented in https://github.com/OneBusAway/onebusaway-client-library/pull/17
• Utility method produces output text optimized for voice interfaces (e.g., Amazon Alexa) that groups prediction information for the same route/headsign - for example "Route 9 UATC to Downtown via 15th St is departing in 5, 35, 85, and 90 minutes", instead of listing each arrival separately and repeating the route/headsign.
• Split out scheduled and real-time predicted arrivals into separate groups, even if they are for the same route/headsign, so users can tell which are scheduled and which are real-time
• If only a single arrival exists for the route/headsign, then just output the normal summary text for that arrival info object
• Updates the unit tests for a small change in the summary text for single arrivals, which was made to make it easier to construct the group summary text

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• [x] Sign the electronic OBA ICLA

• [x] Apply the OneBusAway style template to your code.

• [x] Run the unit tests with mvn test to make sure you didn't break anything

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[coveralls]

Coverage decreased (-0.2%) to 56.711% when pulling 89cfb395d35d5ec1098f7013c63d4204237ef646 on arrivalSummary into 4e6b8dbeefa32733bbb85cdf876abb3ca747a112 on master.