Fixed coding style issues related to the variable naming convention in stout

Review: https://reviews.apache.org/r/28955
Fixed coding style issues related to the variable naming convention in libprocess

Review: https://reviews.apache.org/r/28956
Fixed coding style issues related to the variable naming convention in the routing library

Review: https://reviews.apache.org/r/28957
Renamed getaddrinfo arguments to be more suggestive

Also add missing call to freeaddrinfo when the call fails

Review: https://reviews.apache.org/r/28958
Introduce process::network namespace.

Introduce process::network namespace to encapsulate socket call wrappers
and Socket class.

Review: https://reviews.apache.org/r/28959
Add travis config file for travis-ci.org.

define a travis config file to build debug and release configs on clang
and gcc for linux and osx.

Review: https://reviews.apache.org/r/28683
Fixed regressions in linux link routing library.
Improve travis-ci build matrix