Preventing browser's authorisation dialogue on expired logins

Modified server-side authorisation to not return WWW-Authenticate headers
in 401 response when authentication fails. Closes #44
Merge branch 'master' of github.com:thecapsaicinkid/shoryuken
Use 403 error in place of 401 to avoid browser dialog

API calls while unauthorised will return a 403 error which the client side
code can handle without displaying an ugly browser dialog.
Merge branch 'master' of github.com:thecapsaicinkid/shoryuken