Update mtl Dependency
Add Newissue Command

This patch adds the `newissue` command, which creates a new Issue using
the parameters passed to it. The Subject and Project are required and
you may write the description in your $EDITOR by using the '-e' flag.

* Add the `newissue` command to create a new Issue and print it's ID.
* Add the createIssue API function to create and return a new Issue
  using a JSON object.

* Improve the documentation.

* Modify the postEndPoint function so that it returns the Response.
Fix API Authorization Bug

* Add basic HTTP authorization, using the API key as the username. This
  fixes a bug causing authentication to fail for servers that do not
  accept custom request headers.

* Remove debugging output.