fixes typo
Don't try to generate documentation when the required options aren't set
Updated documentation (jsdoc and removed todo list)
refactoring and improved input validation for rebuildDocumentation

* replaced toAbsolutePath by pathExists / ensurePathExists and p.resolve
* throw a sensible error message when apiDocPath hasn't been set
* removed redundant variabele called 'node'
* removed unused import
fixes readme and change the recommended way to export functions
Merge pull request #6 from Lutger/jsdoc

Do not try to generate documentation when the required apiDocPath option is missing
Merge pull request #7 from Lutger/updated-readme

Updated readme