bump server to fix webView non 0,0 origin bug
added changelog 0.9.160
Update background(secs) to use new send_app_to_background(secs) method

In core.rb, the send_app_to_background method was updated recently, but the calabash_steps file missed the change.
Merge pull request #224 from TeresaP/patch-1

Update background(secs) to use new send_app_to_background(secs) method