Fix shell hyphenation

Prevent the latter part of hyphenated shell terms from being identified as attributes. See, e.g., adobe/brackets#3348. (Notice "cef-clean" and "brackets-shell".) With the fix it looks like this: 

![Brackets](http://f.cl.ly/items/0A1f1T3w243p1v2r3A1G/Screen%20Shot%202013-04-04%20at%205.01.39%20PM.png "Brackets")