Initial mavenization, including example keystore for signing jars

All tests are passing in maven.  The jar file manifest looks good from what I can tell.  I was able to create an intellij project using the "import maven project" feature, and running tests from within intellij works just fine.

I set the version as "1.0-SNAPSHOT".  I figure when there are official releases, folks will want to branch/tag the source and edit the version accordingly.
With pull request #95 merged, I locally built htsjdk (and also picard) with Maven, and I'm successfully using those artifacts in my project (with Gradle). A number of tests failed when building htsjdk, but the tests also failed using Ant.

If the htsjdk team is ready, perhaps this pull request can be merged and the artifact deployed to Maven Central?

In addition to the excellent suggestions by @fnothaft, @heuermh, and @bpow above, I highly recommend using version ranges for all of the dependencies, such as: [1.8.2,). Doing this should help prevent version conflicts with other transitive dependencies for a project using htsjdk. As for TestNG, I think it should be declared with <scope>test</scope> and not marked optional, since it is definitely mandatory for tests. Marking it optional or making it <scope>provided</scope> would be unexpected for users building htsjdk themselves.

I understand that the htsjdk team's time is limited, and that they have other priorities. Having htsjdk and picard in Maven Central would simplify my build process a bit, so I'm happy to help. I can and submit a new pull request with the updated POM if that's preferred.