Remove semver exception handler

As part of the work in SERVER-450, we added a dependency on clj-semver 0.2.0. The trouble is this release doesn't contain an API function that returns a boolean value, we can only get back true or have an exception raised when validating a semver string.

Ideally we'd like to remove the try / catch IllegalArgumentException since it would be better to implement this without an exception handler.

There will need to be a non-snapshot release of clj-semver that contains https://github.com/grimradical/clj-semver/commit/9690467728b7c9266897804c3e11704b185ffa69 for us to accomplish this task.