Initial framework – Tasks for uploading to s3 and returning snap url paths

This basically answers [Issue #1](https://github.com/guardian/thrashers/issues/1) with a grunt script that allows the user to upload to S3 and to get paths to the uploaded content. They do this with the following tasks (all the folderName variables are optional, if you don't provide it, all thrashers will be actioned on)...

- `grunt aws_s3 --folderName=the-name-of-your-embed` Upload a single folder to S3.
- `grunt local --folderName=the-name-of-your-embed` Watch and build locally.
- `grunt remote --folderName=the-name-of-your-embed` Watch, build and upload to S3.
- `grunt paths --folderName=the-name-of-your-embed` Return S3 path and snap url.

This also fixes the `grunt copy` (now `grunt new`) task. Which is otherwise unchanged.

cc @phamann @rich-nguyen @mattosborn

![200](https://cloud.githubusercontent.com/assets/1607666/5072915/f9fcd118-6e75-11e4-8f95-da07f3e56d76.gif)
(This is what it looks like when you upload a json file to S3)
**an** `aws-keys.json`