Add Submission Agreement page

I wasn't exactly sure the approach you wanted to take with the switching off in the controller based on params...

I mocked up an alternative. Basically, whenever the user clicks on any "make a submission" type link, instead of being directed to `new_submission_path`, they get directed to a different path/page I created, submission_agreement.html.haml.

The user clicks on the "I agree, let's write" button at which point they're directed to the submission form. If they don't agree to the terms, they just click "back" and return to the previous page. 

I did a quick search to see how many times the `new_submission_path` link appears, it's like 5 times. So, it wouldn't be a super pain to change those to direct to the submission_agreement page. 

Anyway, I think your way was a bit different. Let me know what you think. If you want to approach this a completely different way than what I began, just give me a hint or two and I'll jump back in :)