Adding Cached and Shallow Healthchecks
Conforming to code conventions
Added javadoc, changed CachedHealthCheck per @bbeck's suggestion, added proxy unit tests
Cleaned up documentation, renamed NumHealthyEndPointsCheck, add forProxy() to ContainsHealthyEndPointCheck
Made HealthCheck constructors private, added forPool static method
Changed healthcheck constructors to protected.
Merge pull request #147 from bazaarvoice/srapp-healthchecks

Adding Cached and Shallow Healthchecks