run ./configure instead of python configure

some versions of nodejs are using shell configure scripts - so all of
them are failing because python is the wrong caller here.
just install npm for nodejs below v0.6.3

since nodejs v0.6.3 npm is provided via nodejs installation.
so it's not required anymore to install npm separately

added tests for is_npm_provided function

:nodejs_stable_version => 'stable'

:nodejs_stable_version => 'stable' is not a valid version any more. the
version stored in facter is expected to be semver.org compatible
Merge pull request #18 from grafjo/patch-1

run ./configure instead of python configure
Merge pull request #17 from grafjo/patch-2

just install npm for nodejs below v0.6.3
Prepare 1.2.0 release
[blacksmith] Bump version