Remove execSync dependency

[tomzx]

execSync is now deprecated.

As mentioned on execSync, both io.js and node.js now support the execSync function.

Please take the time to remove this package dependency to the execSync package.

See node.js or io.js documentation.

Thanks!

[xavi-]

Probably won't remove execSync completely, to maintain reverse compatibility. But I will add a check for the native version.

[CMTegner]

to maintain reverse compatibility

That's what major-increment releases are for ;)