Updating base64url to v2.0.0

[MarkHerhold]

The base64url module changes from 1.x to 2.x only involved a rewrite to TypeScript. It appears that no tests were changed between the versions. Fixes issue #56

[omsmith]

Make it a ^ and you've got yourself a deal

[MarkHerhold]

@omsmith Good to go so long as you squash and merge. :) Thanks!

[MarkHerhold]

@omsmith Thanks! Looking forward to a release. :)
Also, #56 can now be closed.

[daKuleMune]

I noted that this change has not yet been reflected in the npm package. Can you verify if this will fix the deprecation warning in node 7?
DeprecationWarning: Using Buffer without 'new' will soon stop working. Use 'new Buffer()', or preferably 'Buffer.from()', 'Buffer.allocUnsafe()' or 'Buffer.alloc()' instead. at Buffer (buffer.js:79:13) at base64url (/project/node_modules/base64url/index.js:41:21) at jwsSecuredInput (/project/node_modules/jws/lib/sign-stream.js:11:23) ... etc