Travis-CI: also build the skeleton plugin

The skeleton plugin is an example and as such needs to work out-of-the-box.
Make travis build it to ensure we don't break anything.

Signed-off-by: David Wagner <[email protected]>

Author: dawagner

.travis.yml

@@ -9,7 +9,11 @@ before_install:
   - sudo apt-get install -y swig
 
 # how to build
-script: cmake . && make -j && sudo make install && make test
+script:
+  - cmake . && make -j && sudo make install
+  - make test
+  - cd skeleton-subsystem
+  - cmake . && make && sudo make install
 
 notifications:
   email: