AckMate shows files not contained in the TextMate project

[johndouthat]

(This issue the same as topfunky/PeepOpen-Issues#64)

1. Create a project file using File > New Project
2. Drag some files and folders into the project (e.g. drag a few gem folders from your gems directory)
3. Search using AckMate
4. AckMate will show results for files that are not in the project file, but are children of some common ancestor of the items in the project file (e.g. it will show files from gems that you've installed, but that are not included in the texmate project)