@CachedGauge
fix metrics field injection into AOP-advised beans

When injecting metrics into annotated fields of AOP proxied beans, the
bean post processor was attempting to inject the values into the proxy
instance, not the underlying bean.  Since the fields in question didn't
exist, this would cause an error.  Instead, perform the injection at an
earlier phase of bean post-processing, which targets the underlying
bean, not the proxy wrapper.
clean up POM transitive dependencies

* exclude commons-logging, since the SLF4J Commons Logging replacement
  is installed
* don't use the version of JUnit with embedded Hamcrest; instead pull
  Hamcrest in through transitive dependencies
* ensure that all modules of Hamcrest are the same version
* use individual Hamcrest libraries instead of bundle to leverage
  Maven's version conflict resolution
Merge pull request #46 from adammelliott/inject-fields-during-before-initialization

Fix metric injection into AOP-advised beans
Update spring
Merge pull request #47 from adammelliott/pom-fixups

clean up POM transitive dependencies
Merge pull request #49 from ryantenney/cached-gauge

Adds @CachedGauge