install nlopt in travis

Author: John-Colvin

.travis.yml

@@ -50,6 +50,17 @@ matrix:
    - d: dmd-beta
    - d: ldc-beta
 
+addons:
+  apt:
+    packages:
+     - libnlopt0
+
+install:
+ - if [ $TRAVIS_OS_NAME == osx ];
+   then
+     brew install nlopt;
+   fi
+
 script:
   - dub test
   - dub run --root=examples/constraintTest