Describe how to install *latest* node-wot

[danielpeintner]

In some cases it might be useful to install/test node-wot at a given status (on Github) e.g.,

main

npm install https://github.com/eclipse/thingweb.node-wot.git

dedicated branch/commit

npm install https://github.com/eclipse/thingweb.node-wot.git#<branch-or-commit>

certain PR

npm install https://github.com/eclipse/thingweb.node-wot.git#pull/<id>/head

Shall we add some notes about this possibility? Maybe in the development section?