Update package.json to have Karma v0.12

This fixes the error that is currently being presented when attempting to follow the initial setup for the AngularJS tutorial. Error shown is as follows:

npm ERR! peerinvalid The package karma-requirejs does not satisfy its siblings' peerDependencies requirements!
npm ERR! peerinvalid Peer karma@0.10.10 wants karma-requirejs@~0.2.0

npm ERR! System Darwin 13.1.0
npm ERR! command "node" "/usr/local/bin/npm" "install"
npm ERR! cwd /Users/jsantiago/Sites/angular-phonecat
npm ERR! node -v v0.10.26
npm ERR! npm -v 1.4.3
npm ERR! code EPEERINVALID