use ignore_on_server to optimize initial diff
Add gzip_helper which gzips files locally using S3_website config
Gzip files locally in tmp directory before upload is started

It will be necessary to calculate MD5 of gzipped files during diff
calculation.
Use GET bucket req to obtain etags of files and speed up diff calculation
Fix gzip helper
Remove some tests related to gzip from upload spec

Now it's handled by gzip helper.
Fix uploader for cases when site path contains multiple segments
Add gzip_helper rspec tests
Update new-files-for-sydney VCR cassette and test config
Update new-files VCR cassette
Update new-and-changed-files VCR cassette
Update only-changed-files VCR cassette
Update no-new-or-changed-files VCR cassette
Update push.feature scenarios (minor changes in s3_website output)
Update one-file-to-delete VCR cassette
Update s3-and-cloudfront VCR cassette
Update s3-and-cloudfront-when-updating-a-file
Update s3-and-cloudfront-after-deleting-a-file VCR cassette
Update cloudfront.feature scenarios
Update delete.feature scenario