Edited the package.json to include the mocha and benchmark as devDepende...

Added the dependencies to the package manifest.

By including these packages as devDependencies, they'll be included during 'npm install' but not during 'npm install --production'.

In the future, you can automatically add the package name and version info to devdependencies by installing the dependencies with:

npm install [dependency] --save-dev.

To add add production dependencies you can use:

npm install [dependency] --save