travis: try with boost-latest PPA
travis: try with boost-latest PPA

uwsampa/grappa,buaasun/grappa,uwsampa/grappa,uwsampa/grappa,alexfrolov/grappa,alexfrolov/grappa,alexfrolov/grappa,alexfrolov/grappa,buaasun/grappa,buaasun/grappa,uwsampa/grappa,uwsampa/grappa,buaasun/grappa,buaasun/grappa,uwsampa/grappa,uwsampa/grappa,alexfrolov/grappa,buaasun/grappa,alexfrolov/grappa,alexfrolov/grappa,buaasun/grappa