Add `ag-dired` and `ag-dired-project`.
Fix `ag-dired` adding buffers to `dired-buffers` which breaks `dired-up-directory`.
Rename ag-dired-project to ag-project-dired
Add -regexp flavours
Merge pull request #32 from Fuco1/ag-find-regexp

Add `ag-dired` and `ag-dired-project`.