Relative absolute

#23, #26, #31

I added a new param `context` in vatican app. All the paths in application will be computed relative to this param.

If `context` is setted, in constructor then it must be an absolute path and all the paths, which are not absolute will be computed relative to it.

If `context` is not setted then `context` will be considered current working directory.

For node version which do not support `isAbsolute` function I defined this function as component of `path` module.