Uniform Condition syntax
Refactor Node props and targets

Better names for props and targets and improved error handling.

Breaking Changes:
  * Renamed node properties
    * DefaultNodePath => GlobalNodePath
    * DefaultNpmPath => GlobalNodeModulePath
    * CustomNodePath => LocalNodePath
    * CustomNpmPath => GlobalNodeModulePath
  * Renamed `EnsureNpm` target to `EnsureNodeModules`
Update module packages to use new Node properties and improve error
handling.

Fixes #5
Implement support for running npm modules with a local NodeJS installation
Update example
Bump versions to 0.3.0