travis-ci: Use gradle 2.7
travis-ci: Use gradle 2.7

Flowdalic/Smack,esl/Smack,vanitasvitae/smack-omemo,igniterealtime/Smack,vanitasvitae/Smack,cjpx00008/Smack,andrey42/Smack,vanitasvitae/smack-omemo,vanitasvitae/smack-omemo,esl/Smack,igniterealtime/Smack,hy9902/Smack,hy9902/Smack,hy9902/Smack,andrey42/Smack,vanitasvitae/Smack,annovanvliet/Smack,andrey42/Smack,annovanvliet/Smack,igniterealtime/Smack,Flowdalic/Smack,cjpx00008/Smack,vanitasvitae/Smack,Flowdalic/Smack,esl/Smack,cjpx00008/Smack,annovanvliet/Smack