Return errors to callback if a server cannot start

EACCES, EADDRINUSE
Factored out common server starter logic.
Streamlined Getting Started.
Updated getting started download link.
Reworked logger, now configurable.

Closes #6.
Merge branch 'master' of github.com:RupertJS/rupert

Conflicts:
	README.md
Merge pull request #7 from DavidSouther/master

Some docs, logging, exception handling updates.