test: Add Travis-CI continuous integration
test: Add Travis-CI continuous integration

Configure, build and run test suite on GCC and Clang.

envytools/envytools,karolherbst/envytools,karolherbst/envytools,envytools/envytools,pierremoreau/envytools,pierremoreau/envytools,envytools/envytools,karolherbst/envytools,envytools/envytools,karolherbst/envytools,pierremoreau/envytools,MoochMcGee/envytools,envytools/envytools,karolherbst/envytools,MoochMcGee/envytools,MoochMcGee/envytools,MoochMcGee/envytools,pierremoreau/envytools,pierremoreau/envytools,MoochMcGee/envytools