Signature calculation has now moved out from being a package to
top-level as a layered mechanism.
In case of payload calculation with body, go-routines are initiated
to simultaneously write and calculate shasum. Errors are sent
over the writer so that the lower layer removes the temporary files
properly.
- Upon first time invocation ``minio controller`` would create access keys and secret id
- Upon request passing 'keys' arg ``minio controller`` would provide the keys
- Add colorized notification