Create a new *ag* buffer for new searches. Closes #18
adding a usage section to the readme
adding ag-kill-buffers and ag-kill-other-buffers
adding an ag-reuse-buffers variable. #19
adding a table of contents
releasing version 0.25
Fixing a crash when regenerating search results

Since Emacs does dynamic binding by default, returning this:

(lambda (mode-name) (ag/buffer-name string directory regexp))

does not evaluate `(ag/buffer-name string directory regexp)` in the
context of `ag/search`. Instead, we get an error about string being a
void variable. We force evaluation of the `ag/buffer-name` call to fix
this.