Set transport with url (#220)

* set transport with uri/url

* only set websocket if uri is set and is not http, postinstall fix

* add prepare directive in package.json for loading/building directly from git

* Add run build on postinstall

* Remove prepare script and add postinstall-build dep

* regex and logic fix

* use separate url option

* predefine url

* url defaults to not set to work with previous configuration methods

* null string instead of boolean value

* Update doc

* Update steem.api test