[refactor] Refactor the procedure used to build the Engine.IO client

Do not use the `engine.io-client` dev dependency to build the client. Clone the repo, checkout to the latest tag and build from there instead.
This gives more flexibility and ensures that the build is done against the latest available version.
[deps] Add a utility to automate the build of the SockJS client
[doc] Add build/update instructions for the SockJS client
[feature] Add a script to automate the build of the shipped client-side frameworks
Merge pull request #167 from lpinca/add/automated-frameworks-generation

Automate the build of the shipped client-side frameworks