When installing Meteor, installer should update path even if Meteor is already installed

[zodern]

If for some reason Meteor is installed but isn't included in the path (for example, you installed Meteor with the old npm installer that had a npm bin file, and updated the meteor package to a new version that doesn't have it), it would be nice if the installer could check if the path has meteor in it, and if it doesn't it fixes it.

[zodern]

Another option is to add a command to the meteor-installer cli for updating the path.