Added method to set 'mutable-content' to 1. Fixes #321, #328.

[cemcatik]

[cemcatik]

Any idea how to resolve the timeout error? It's not related to this changelist and I can't repro locally.

Results :

Tests in error: 
  sendOneSimple(com.notnoop.apns.integration.ApnsConnectionTest): test timed out after 2000 milliseconds

Tests run: 112, Failures: 0, Errors: 1, Skipped: 3

[grippy]

@cemcatik - One minor issue.

@matzew It looks like you merged the last PR on this repo. Are you still maintaining it? Any idea what we need to do to get this error resolved so we can merge this and publish a new release?

[satishbotla]

any one merging this pr?