Changed color of selected area in helm

Turns out that leuven-theme along with f.lux makes the selected item in
helm near impossible to see. Changed it to a cyan, which is a bit ugly,
but at least I can see it.

init.org

@@ -501,6 +501,8 @@
            helm-grep-default-recurse-command
            "ack -H --no-group --no-color %e %p %f"))
 
+   (set-face-attribute 'helm-selection nil :background "cyan")
+
    (helm-mode 1)
    (helm-projectile-on)
    (helm-adaptive-mode 1)