(SERVER-29) exclude BouncyCastle jars from uberjar

Yo dawg, JRuby bundles the BouncyCastle .jars in its .jar.  Avoid using these,
since this project defines its own dependency on BouncyCastle directly.
(SERVER-29) Add comments about BC jars in JRuby for uberjar
Merge pull request #254 from cprice404/SERVER-29/no-bc-jars-in-uberjar

(SERVER-29) add comment about BC jars in jruby jar