Feature Request: Allow an ignore argument

Basically it would be nice to be able to define subdirectories/files not to sync up to the bucket.  

For example: .git, .idea etc

Presently to only upload what you want, you'd have to stage in a subdirectory and then perform the command from that directory.  Aws cli's s3 sync has the following syntax for reference:

`aws s3 sync . s3://mybucket --exclude ".idea/*"`