Adding .travis.yml for CI support.

[kingtaurus]

Adding support for travis-CI (continuous integration of the build). Building completes;

Build platform is trusty (Ubuntu 14.04 LTS); Compilers: gcc (Ubuntu 4.8.4-2ubuntu1~14.04) 4.8.4, clang version 3.5.0 (tags/RELEASE_350/final)

Files (plus changes): .travis.yml: Build configuration; src/build_options.cmake: Added the compiler flag -Wno-old-style-cast to allow for build to complete properly while on travis-CI.org (4MB log limit);