Ruby 530 kerberos on JRuby

NOTE: There are some more tests needed but I wanted to get a code review started on this. I'll update the PR with more tests for replicasets, in particular.

This pull request consists of a java extension for using the java sasl package. The jar is checked into the repo but you can compile it by invoking the jsasl rake task:

    rake compile:jsasl

There are some additions to the authentication module in order to allow authentication using the java extension, in addition to a module called Sasl / GSSAPI that uses the java extension.

The URI parser has been updated to include GSSAPI authentication options, gssapiservicename and canonicalizehostname. (Plus tests)

In order to test, you must:

1. Use JRuby
2. Set up a SASL config file that references a keytab file
3. Set the following environment variables:
	- MONGODB_GSSAPI_USER
	- MONGODB_GSSAPI_HOST
	- SASL_CONFIG_FILE