MoPub sample, fixed libGDX example

Btw, interstitial.loadAd() in didDisappear and didExpire - bad idea, bacause initiate loop loading, about 10 requests per second. Useless cpu and network loading.
setUserInteractionEnabled(false) deleted because ads must be clickable.
Merge pull request #5 from semtiko/patch-1

MoPub sample, fixed libGDX example