accept linkDependencies in package.json, so test will work again

 * bump version to 0.1.3-medesso.0
 * gruntfile: use single quotes
 * .gitignore: add gruntlink_symlinks (default smylink dir)
 * link.js: add default values for prefix & linkDependencies
 * linker.js:
   ** fixed if condition in mkDirP (error handling was wrong)
   ** use strict equality (  === 'triple e') to check type of function (JSLint)
   ** use PackageName instead of DirectoryName of Package to create the Symlink
 * link_helper.js - findLinks:
   ** accept non-existing dependencies in package.json
   ** accept linkDependencies in package.json, again (original use-case)