Add utterance 'stop {number}'

[vikram31291]

Please make sure these boxes are checked before submitting your pull request - thanks!

• [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
• [x] If you have multiple commits please combine them into one commit by squashing them.

[coveralls]

Coverage remained the same at 53.759% when pulling 0a61951dd3d099f2cc3892c4f852b09d17950f56 on vikram31291:vikram/addStopUtterance into 22b9fd944849c9b74314099ef3a3b1c52c538cc9 on OneBusAway:master.

[coveralls]

Coverage remained the same at 53.759% when pulling 0a61951dd3d099f2cc3892c4f852b09d17950f56 on vikram31291:vikram/addStopUtterance into 22b9fd944849c9b74314099ef3a3b1c52c538cc9 on OneBusAway:master.

[barbeau]

ICLA manually confirmed :+1:

Thanks @vikram31291!