Ability to deploy individual bundles to different buckets.

This pull request implements the ability for someone to specify a different destination bucket for particular bundles. Bundles who have been targeted at a specific destination bucket will be excluded from the deployment to the bucket specified in the `awsS3Bucket` setting in build.sbt.

To target a bundle at a particular bucket, you use an arrow designation in the bundle file. So, as an example:

```
primary-scripts
script1.js
script2.js
script3.js

aux-scripts->aux.frmr.me
aux1.js
aux2.js
```

In the above example, the primary-scripts bundle would be deployed to the bucket defined in `awsS3Bucket` and the aux-scripts bundle would be deployed to a bucket named `aux.frmr.me`.

Naturally, these two buckets must both be accessible from the same AWS account with the same access key and secret.