Improve port and process management
Add ReuseAddr's flag for isBindable.
Add isBindableByProc which uses /proc/net to search available port.
Change userPorts-range from [49152..65535] to [5001..32767].
 ([49152..65535] is os-port-searching area.)
Add cleanUpProcesses which stops process-groups when test is finished.
Add runSandbox and withSandbox funtions for unit-test
Change ErrorT to ExceptT
Fix compile-warning
Add .travis.yml