Remove piston dependency

Closes https://github.com/PistonDevelopers/piston-examples/issues/84
Remove piston dependency

Closes https://github.com/PistonDevelopers/piston-examples/issues/84
Merge branch 'master' of https://github.com/bvssvni/piston-examples
Merge pull request #86 from bvssvni/master

Remove piston dependency