re-ordered sessionSummary properties for clarity. Added default of UNKNOWN for deviceId
added check for PhoneGap object in windows scope to isPhoneGap method. this object will be available before window.device is set.
moved useragent parsing logic into its own method
initial re-ordering of properties caused sessionStartTime to be undefined.
working issues in platform detection logic
Merge pull request #25 from apigee/USERGRID-2485

Usergrid 2485: Fallback to default when platform detection fails in JS SDK