added real support for multiple installed versions of nodejs

It was not possible to install multiple different versions of nodejs
e.g.:
nodejs::install{"v0.10.20": version => "v0.10.20", make_install => false}
nodejs::install{"v0.10.19": version => "v0.10.19", make_install => false}

* fixed double resource definition errors
* an archive is extracted into /usr/local/node/node-$version
* nodejs::install symlink of nodejs contains the version
* class nodejs is responsible for symlink $target_dir/node
* enhanced ./configure to install nodejs into /usr/local/node/node-
$version instead of /usr/local
* fixed puppet lint issues
* fixed node symlink issue with non semver versions
* improved default values handling
* refactored nodejs class spec
* fixed typo inside README.md
* fixed broken spec for define nodejs::install
* enhanced spec for define nodejs::install

Known limitation: just a single nodejs::install define of versions below
v0.6.3 is supportet!
Merge pull request #20 from grafjo/patch-4

added real support for multiple installed versions of nodejs