Merge pull request #242 from trishagee/JAVA-1391

JAVA-1391: Javadoc for driver-core, first batch of documentation
JAVA-1391: Javadoc for AsyncCompletionHandler
JAVA-1391: Javadoc for NativeAuthenticationHelper
JAVA-1391: Javadoc for public classes that should not be considered part of the public API.
InternalStreamConnectionSpecification updates

The reading of headers now has the messageId explicitly set.
Update README.md

Updated Maintainers and added travis build icon
Fix explain tests for 2.7-nightly
Added tryNext() for tailable cursors

JAVA-1255
Removing gradle.properties
Merge branch '3.0.x' into crud

Conflicts:
	driver-core/src/main/com/mongodb/operation/Query.java
	driver-core/src/test/unit/com/mongodb/operation/QuerySpecification.groovy
Update tryNext() to findModel
Update priavte insert method args
Removed FindAndRemove<T> from FindAndRemoveOperation

JAVA-1215