in travis, build for osx also

Author: cdunn2001

.travis.yml

@@ -31,7 +31,6 @@ install:
 - export PATH="${PWD}"/build:/usr/local/bin:/usr/bin:${PATH}
 - echo ${CXX}
 - ${CXX} --version
-- which valgrind
 addons:
   apt:
     sources:
@@ -44,6 +43,7 @@ addons:
     - valgrind
 os:
   - linux
+  - osx
 language: cpp
 compiler:
   - gcc