change crypto library reference

[nicolaslawdune]

fixes crypto library reference #1071

[coveralls]

Coverage remained the same at 85.0% when pulling 5ca0432 on Synapsium:1.0ES6 into b882ea2 on ethereum:1.0ES6.

[frozeman]

As you dont add the package itself to the package.json, i wonder if that still works in node.js, and the browser? Can also please build the browserify files and test it in the browser?

[frozeman]

I made the change myself, thanks for the PR anyway