Local Install Instructions missing a command, could be more straightforward

[boubascript]

I'd like to make a Pull Request with minor changes to the CONTRIBUTING doc so it is easier to follow:

• It should mention that npm install has to be run before attempting to build the extension the first time.
• Grunt is listed as a prerequisite, but the npm package page is linked and grunt is already listed in package.json which is slightly misleading. It seems the actual prerequisite meant is the grunt-cli package according to the grunt site, since the extension uses grunt 0.4. Though anyone can figure this out by clicking the main link from the npm page, it tripped me up when first attempting to build. Assuming you don't want to add grunt-cli itself as a dependency, it might be more straightforward to directly link to the grunt site and just add the command from that page npm install -g grunt-cli in the doc itself.

Any feedback is greatly appreciated.

[ayao451]

Is this issue still open? I have made the changes and updated a few links and I want to push it!