TravisCI: enable osx builds
diff --git a/.travis.yml b/.travis.yml
index 71f8080..45bbd1f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,10 +1,25 @@
 language: c
 
+os:
+  - linux
+  - osx
+
 env:
-  - BUNDLEDLIBTOM=--disable-bundled-libtom WEXTRAFLAGS=-Werror
-  - BUNDLEDLIBTOM=--enable-bundled-libtom
-  - MULTI=1
-  - NOWRITEV=1
+  matrix:
+    - BUNDLEDLIBTOM=--disable-bundled-libtom WEXTRAFLAGS=-Werror
+    - BUNDLEDLIBTOM=--enable-bundled-libtom
+    - MULTI=1
+    - NOWRITEV=1
+
+# TODO: remove this section when libtomcrypt compiles on OSX: https://github.com/libtom/libtomcrypt/issues/82
+matrix:
+  exclude:
+    - os: osx
+      env: BUNDLEDLIBTOM=--disable-bundled-libtom WEXTRAFLAGS=-Werror
+    - os: osx
+      env: MULTI=1
+    - os: osx
+      env: NOWRITEV=1
 
 compiler:
   - gcc
@@ -20,6 +35,10 @@
     - libtomcrypt-dev
     - libtommath-dev
 
+
+install:
+  - if [ "$TRAVIS_OS_NAME" = "osx" -a "$BUNDLEDLIBTOM" != "--enable-bundled-libtom" ]; then brew update > /dev/null && brew install libtomcrypt libtommath ; fi
+
 script:
   - autoconf && autoheader && ./configure $BUNDLEDLIBTOM CFLAGS="-O2 -Wall -Wno-pointer-sign $WEXTRAFLAGS" --prefix=$HOME/inst
   - test "$NOWRITEV" && sed -i s/HAVE_WRITEV/DONT_HAVE_WRITEV/ config.h || true