Knex & Bookshelf update

I used [david-dm](http://david-dm.org) to check for & update the latest dependencies for all modules (made sure to explicitly specify which to use). I also added mysql as a client, since I'm sure people are looking to use it but haven't had it installed... it shouldn't be any overhead to have it defined as a dependency if it's not used (other than a few megs of storage), and it probably will help folks who are looking to use it.
 
Then I also updated to the latest stable Bookshelf (0.5.x) & Knex (0.4.x), which gets rid of an issue people have been seeing where the `try/catch` was wrapped around the entire Client initialize, obscuring an error when they either didn't have mysql or if their sqlite3 wasn't playing nicely with their OS... Also, it'll be easier to continue to pull in any updates to these libraries that come along.