Added a lightweight form of getApplicationInstances() that only makes one REST call instead of many. Made both forms of getApplicationInstances() return an empty list if the app is in the STARTED state but has not yet finished staging, instead of throwing an exception in this case.
Changed getApplicationInstances() return null instead of empty list when app has not finished staging.
Fixed tests.
Merge pull request #79 from scottfrederick/instances

Added a lightweight form of getApplicationInstances()