chore(docs): Update readme instructions (#506)
chore(docs): Update readme instructions (#506)

Include troubleshooting steps for "Cannot find namespace 'firebase'"
Update versions and syntax to match latest angular-cli output.
maneesht/angularfire2,maneesht/angularfire2,maneesht/angularfire2,angular/angularfire,angular/angularfire,angular/angularfire,angular/angularfire,maneesht/angularfire2