Update asset_cloud to internal version

This way we can extract it from the codebase
Update url_for to take options
Remove .document file
Update license
Update gemspec

Add Gemfile
Remove VERSION file
Add *.gem to gemspec
Don't commit Gemfile.lock
Move bucket regexp test to base_spec
Use MATCH_BUCKET in asset_cloud/base
Ignore Gemfile.lock
Don't use file-relative requires
Merge pull request #1 from Shopify/update-to-internal-version

Update to internal version