Revert "Remove libevent extension from travis for now"
Revert "Remove libevent extension from travis for now"

This reverts commit 3add2c3a4b7ba3734fd33923523155a64c277161.

cesarmarinhorj/react,nemurici/react,naroga/react,cesarmarinhorj/react,ericariyanto/react,sachintaware/react,FireWalkerX/react,dagopoot/react,ympons/react,cystbear/react,ympons/react,sachintaware/react,cystbear/react,nemurici/react,reactphp/react,ericariyanto/react,dagopoot/react,krageon/react,krageon/react,FireWalkerX/react,naroga/react