Run the integration with GOMAXPROCS=2
Run the integration with GOMAXPROCS=2

Multiple entries in the .travis.yml under the environment section will
produce multiple builds with each environment.  Each entry is space
delimited.  To test races in #46, we want to run the integrations with
GOMAXPROCS=2 instead of run the integrations with AMQP_URL then the unit
tests with GOMAXPROCS=2.

beni55/amqp,aviau/amqp,z00223295/amqp,vektra/amqp,vektra/amqp,StephaneP/amqp,z00223295/amqp,gcnonato/amqp,TeamFairmont/amqp,ChannelMeter/amqp,aviau/amqp,akrennmair/amqp,akrennmair/amqp,beni55/amqp,gcnonato/amqp,streadway/amqp,StephaneP/amqp,streadway/amqp,TeamFairmont/amqp,ChannelMeter/amqp