fixed npm install for nodejs versions below 0.6.3

Solves known limitation:
* Just a single nodejs::install define of versions below v0.6.3 is
supported
added default symlink for npm again
Merge pull request #23 from grafjo/patch-7

added default symlink for npm again
Merge pull request #22 from grafjo/patch-6

fixed npm install for nodejs versions below 0.6.3
Add Johannes as author
Prepare 1.5.0 release
[blacksmith] Bump version