Merge pull request #198 from bvssvni/master

Updated symlink info
Added link to piston-workspace

Closes https://github.com/PistonDevelopers/piston/issues/199
Merge pull request #201 from bvssvni/master

Updated symlink info
Update examples
Merge pull request #202 from gmorenz/fix-examples

Update examples
Minor improvements to `Event`, `Key` and `Button`

* Made `Button` usable with hash maps
* Added Ord for `Key`
* Deriving traits for `Event`
* Inlined primitive conversions of `Key`