Updating plugin to work with CakePHP 3

[akkaweb]

I wanted to use this great plugin in my applications that use CakePHP 3 to take advantage of Chosen. Since a 3.0 version was not yet available and instead of waiting or creating another, I decided to just upgrade this to work with CakePHP 3. I have been using it in my applications and I will continue using it everything I need. Before moving foward with more additions, I wanted to bring this up to you, so you can look into it to make sure I am heading in the right direction. I have updated the README file to reflect these changes and make sure users can set the plugin successfully. TestCases are yet to be created.

[akkaweb]

Also, I wanted to bring up to you that, this is my first ever Pull Request. I noticed it says "akkaweb wants to merge 1 commit into paulredmond:master from akkaweb:akkaweb/3.0". However, that is not my intention as this is a totally new branch. Not just some changes. You can do how you feel is right.

[paulredmond]

@akkaweb sweet. I've been focused more on Laravel lately, so I will keep an eye on this PR once you get test coverage and passing CI build I will review it. Thanks!

[akkaweb]

@paulredmond I should be able to create those tests this weekend. I will keep you posted. Thanks!