Make extra sure connections can never be sslv3 closes #1957

If I followed the stack correctly, it looks like in the configureCipherSuites method, in the CertTrackingSslEngineSource class, we retrieve the cipher suites enabled here and call setEnabledCipherSuites() on the SSLEngine. With these changes, we are no longer supporting 256-bit key sizes. 
It sounds like 128 bits is quite sufficient for security already, from what I've read (here)[https://security.stackexchange.com/questions/14068/why-most-people-use-256-bit-encryption-instead-of-128-bit]. Are there any further implications for limiting ourselves to a single cipher suite now?
Otherwise, LGTM!