Add meteor 0.9.4

Meteor has a self-update function, [disqualifying it from the core homebrew tap](https://github.com/meteor/meteor/issues/16). See also ["We don't like tools that upgrade themselves"](https://github.com/Homebrew/homebrew/wiki/Acceptable-Formulae#user-content-we-dont-like-tools-that-upgrade-themselves) in the [Acceptable Formulae](https://github.com/Homebrew/homebrew/wiki/Acceptable-Formulae) guide.

This formula installs meteor 0.9.4 to the homebrew cellar.