Teach travis to build multiple configurations. This is done by using
TravisCI's build matrix feature. We set an environment variable to
indicate which configuration we want.

Unfortunately there doesn't seem to be a direct way to have options
set with -D to CMake be set instead with environment variables. So
instead we use a wrapper script to set the configuration.
Fix running of API tests when BUILD_STATIC_BIN is enabled.
Try to fix the broken STATIC_BINARY build in Travis when using clang.
It's most likely an issue with the old clang and ld on Ubuntu 12.04LTS
Disable python interface when building configurations that only
build libstp as a static library otherwise we get configuration
errors.
Merge pull request #125 from delcypher/multiple_travis_configurations

Teach travis to build multiple configurations. This is done by using