Maintenance Release 0.1.1

This is a cleanup and maintenance release. Changes include:

• Create or check destination directory before copying
• Use preallocated buffers to avoid allocations
• Added documentation about contributing and project goals
• minor cleanups and documentation improvements

First release

In this first release, psync can copy a file tree concurrently from a source to a destination directory. It acts a lot like "cp -a" on Unix, but uses concurrency to speed up the transfer.

The release is quite well tested, but only under Linux (Debian 9 and CentOS 7).