send raw value in onChange callback function

[viniciusdacal]

I had some errors running both, yarn install and npm install, and npm suggest to replace "babel" for "babel-cli":

You have mistakenly installed the `babel` package, which is a no-op in Babel 6.
Babel's CLI commands have been moved from the `babel` package to the `babel-cli` package.

    npm uninstall babel
    npm install babel-cli

See http://babeljs.io/docs/usage/cli/ for setup instructions.

I took the freedom to add a yarn.lock file, for those whom wants to use yarn
I updated the tests for the new format that function mask is returning.

[viniciusdacal]

related to issue #4

[jsillitoe]

Thank you. Merged!