Add AWS ElastiCache (Memcache) CacheAdaptor Implementation

I've added two `CacheAdaptors` to the project:
 * `ElastiCacheCCAdaptor`, and
 * `IndexedElastiCacheCCAdaptor`

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The "Indexed" adaptor keeps a map (in cache) of from table names to sets of keys in those tables.  This allows `CacheAdaptor`'s `int count(String tableName)` and `void remove(String tableName)` methods to be implemented.

With the vanilla `ElastiCacheCCAdaptor` those two methods throw `UnsupportedOperationException`s.  However, neither of these methods are called by `DynamonitoMapper`, so they probably aren't necessary.  In our project we're going to use `ElastiCacheCCAdaptor`, since "Indexed" adaptor has to get/set a table full of values for all but value get operations.

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Other than that, I've contributed some general clean-up, which you can take or leave:
 * Commented out failing/unfinished tests
 * Added JUnit dependency for testing
 * Split integration & unit tests (integration tests run with `mvn verify`, unit tests with `mvn test`)
 * Added maven-surefire-plugin and maven-failsafe-plugin for running integration/unit tests separately, and reporting the results
 * Removed `GettingStarted`, since it referred to classes in src/test, which weren't accessible from src/main.