Generate Typescript Typings via JsDoc

[samparsky]

• Adds typings to the js-libp2p-secio module
• Add typings generation to travis.yml
• Include typings test

[damien-white]

I could write them out manually and then distribute it via DefinitelyTyped if you like. I would be more than happy to help. I would imagine it shouldn't cause any issues and all of the types seem to be pretty straight forward; I've worked with crypto libraries like nacl and libsodium as well as node-forge and the native Node and Browser Crypto APIs.

[vasco-santos]

FYI: We have some typescript support decision updates on libp2p/js-libp2p#659.

[Stebalien]

(closing due to package deprecation)

[Stebalien]

(closing due to package deprecation)