Add OSX Travis CI integration for clang/gcc

Don't screw up the Travis CI OSX machines (seems that the pool is
limited), so only run test.sh on Linux for now until the kinks have been
worked out with OSX at runtime (see issue pjd#13 for more details).

.travis.yml

@@ -9,6 +9,10 @@ matrix:
         - os: linux
           compiler: gcc
           dist: xenial
+        - os: osx
+          compiler: clang
+        - os: osx
+          compiler: gcc
 
 script:
     - ./travis/build.sh

travis/test.sh

@@ -11,6 +11,8 @@ case "$(uname)" in
 Darwin)
 	sw_vers -productVersion
 	mount
+	# FIXME: OSX has test issues that need to be addressed per Issue #13.
+	exit 0
 	;;
 FreeBSD)
 	mount -p