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

This currently has a dep on a SNAPSHOT of clj-http-client, so shouldn't be merged yet.
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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
So part of the deal here is that if you don't have a predicate, cursive can't recognize and mark the test status in the IDE.  The cursive author says that that has something to do with the underlying implementation.  It's kind of wonky, but it is useful enough that I'm willing to jump through the minor hoop in order to make it work with cursive.

I'm open to changing it to some other predicate if anyone has a suggestion, but `(is false)` won't work.