Build against Java 1.7
Build against Java 1.7

The sample code uses generics and by default
mvn builds with 1.3, which doesn't support generics.
This patch sets mvn to use 1.7.

Signed-off-by: Joe Buck <a95e51950b61b017a762bcc8a962bac0b1a073a0@gmail.com>

four2five/simple-yarn-app