Add `moment` as a project dependency

The moment library makes it easy to diff the timestamps which are used for
determining connection expirations so it's been added as a project
dependency.
Fix SFDC connection timeouts

This commit fixes connection timeout issues by expiring the outstanding
connection to salesforce after some interval. The connection state is
checked with each request and a new connection will be spawned if it has
exceeded the max connection age limit.
Merge pull request #3 from nutanix/bug/connection-timeouts

Bug/connection timeouts