v0.5.0

• Added client caching to reuse an existing s3 client rather than creating a new one for each upload. Fixes #6
• Updated the maxPartSize to be a hard limit instead of a soft one so that generated ETAG's are consistent due to the reliable size of the uploaded parts. Fixes #7
• Added a changelog.md file. Fixes #8
• New feature: concurrent part uploads. Now you can optionally enable concurrent part uploads if you wish to allow your application to drain the source stream more quickly and absorb some of the backpressure from a fast incoming stream when uploading to S3.