Added main property in package.json

Since the main chancejs library file is not named index.js or index.node (see http://nodejs.org/api/modules.html#modules_folders_as_modules ), this is needed so that the library can be found via require().
Updated README.md to reflect that the current node module name is lowercase.
Merge pull request #4 from qjcg/node-module-fix

Node module fix