Add some missing protocol commands

[jd84]

I added some missing protocol commands:

• reserve with timeout
• bury
• touch
• release

All changes I made are backwards compatible.

I added also an example for any new feature and completed the test as you did @schickling. It would be awesome if you can review my pull request and merge it. If you merge it and release a new version on crates.io I'll drive the library to completion. There are more protocol commands that are not implemented yet.

If you've any suggestion, feel free to contact me.