Add .idea to .gitignore and change file format from dos to unix
Do not try to nvm install a node version that is already installed.
Set the delete on task's config closure to be the extension.

This allows the config closure to directly manipulate the extension
without having to refer to the passed in argument.

Also converted file from dos to unix file format.
Add wrapper method so task config looks the same as plugin config.

This allows for the configuration of a task using the same syntax
as when configuring the the plugin.
Merge pull request #8 from johnrengelman/node-use

Usability Updates - node version installation, task configuration