spacemacs: Use helm-project-ag for s-g
spacemacs: Use helm-project-ag for s-g

replace helm-projectil-grep with helm-projectile-ag as helm-ag now
supports detection of search finish.

Signed-off-by: Ratheesh S <f847af0ee3590f4912d169b886f309989d9e4c2e@gmail.com>

ratheesh/dot-files,ratheesh/dot-files