update readme with some more info

Signed-off-by: Michael Diener <dm.menthos@gmail.com>
adjusted some error in the js source file

Signed-off-by: Michael Diener <dm.menthos@gmail.com>
changed name of the file operations array to something more readable

Signed-off-by: Michael Diener <dm.menthos@gmail.com>
added two new error classes

Signed-off-by: Michael Diener <dm.menthos@gmail.com>
added the building branch of grace

Signed-off-by: Michael Diener <dm.menthos@gmail.com>