Added volume to example

Closes https://github.com/RustAudio/dsp-chain/issues/69
Added volume to example

Closes https://github.com/RustAudio/dsp-chain/issues/69
Fixed timer in example
Merge branch 'master' of https://github.com/bvssvni/dsp-chain
Merge pull request #72 from bvssvni/master

Added volume to example