Updating Guava dependency from 16.x to 21.x

[apolaskey]

All 40 tests passed; installed locally and ran with project and report was successfully generated with a backing Guava dependency of 21

[apolaskey]

Should note also bumped up minor due to the huge jump in the guava dep.

[kunal546]

I approved this but found out that Guava 21 needs JDK 8 and this project is still using 7.

https://github.com/google/guava/wiki/Release21

Can you please test building this with 1.7 and running it from an application with 1.7 runtime? We may need to upgrade the jdk.version to 1.7.

[apolaskey]

@kunal546 Just to be clear your asking for a PR with the plugins updated for JDK8?

[apolaskey]

@kunal546 Two routes we can take here; update the Maven target to 1.8 or downgrade to Guava 20.0 to preserve JDK7 compat.

For now I'll submit a PR to master for the POM updates to target JDK8; what's strange is that it built fine with the 1.7 target (could be that what's used from Guava isn't requiring it).