Added method-override to fix missing dependency issue.

[jcelder]

It seems there is a missing dependency in the base version of this project. When running nodemon after initial install, I received the following error:
`module.js:538
throw err;
^

Error: Cannot find module 'method-override'
at Function.Module._resolveFilename (module.js:536:15)
at Function.Module._load (module.js:466:25)
at Module.require (module.js:579:17)
at require (internal/module.js:11:18)
at Object. (/Users/josh/dev/phase3/auth-snapshot/src/server.js:4:24)
at Module._compile (module.js:635:30)
at Object.Module._extensions..js (module.js:646:10)
at Module.load (module.js:554:32)
at tryModuleLoad (module.js:497:12)
at Function.Module._load (module.js:489:3)`

Fixed by adding 'method-override' to package.json.