Various bug fixes

Error during npm install:

The current version on npm does not install correctly. It fails on the
browserify command:

browserify -d -o node-xmpp-browser.js lib/node-xmpp-browserify.js

The error browserify gives is:

Error: Cannot find module: "JID" from directory

This is caused by an incorrect require in lib/node-xmpp-browserify.js
which I fixed in this commit.

I tried testing the browserified generated code but in my browser the example code did not work (could not find dns). I do not know if this was supposed to work already.

Error when connecting as component:

- Component does not inherit anymore from connection
- Connection now adds the correct stream attributes in case of a component connection.

Incorrect prototype of the Mechanism:

- Fixed