(SERVER-71) Add support for configuring http client ssl protocol

This commit does the following:

* Upgrade us to the latest version of clj-http-client, which includes
  a default list of legal ssl-protocols and makes them configurable
* Add a new `http-client` settings section, in which you can configure
  the legal ssl-protocols and cipher suites for any http client requests
  that are issued by Puppet Server
not strictly, no, just kind of wanted to mix in a test case where there was more than one protocol specified.