Upgraded travis testing to openjdk7
Upgraded travis testing to openjdk7

Expect: 100-continue behaviour is broken in openjdk6 (see
https://bugs.openjdk.java.net/browse/JDK-8012625).
Travis does not support any other jdk6 (see
http://docs.travis-ci.com/user/languages/java/#Testing-Against-Multiple-
JDKs).
So moved to test with openjdk7 instead.

BugId: 48522

cloudant/java-cloudant,cloudant/java-cloudant,cloudant/java-cloudant