travis: Install eigen3 via package from Ubuntu repository

.travis.yml

@@ -129,12 +129,12 @@ before_install:
                                libmedc-dev			\
                                asciidoc
 
-       #Install Eigen 3.3.3 to reduce compiler warnings
-       curl -L "http://bitbucket.org/eigen/eigen/get/3.3.3.tar.gz" | tar xvz && cd eigen-*
-       mkdir build && cd build
-       cmake -DCMAKE_C_FLAGS_RELEASE=-DNDEBUG -DCMAKE_CXX_FLAGS_RELEASE=-DNDEBUG -DCMAKE_BUILD_TYPE=Release -DCMAKE_VERBOSE_MAKEFILE=ON ..
-       sudo make -j2 install
-       cd ${TRAVIS_BUILD_DIR}
+       # Make sure dpkg is upgraded for Ubuntu 14.04 (required for eigen3)
+       sudo apt-get install -y dpkg
+
+       # Use latest Eigen3 package
+       curl -L http://security.ubuntu.com/ubuntu/pool/universe/e/eigen3/libeigen3-dev_3.3.4-4_all.deb -o libeigen3.deb \
+            && sudo dpkg -i libeigen3.deb
 
        #Install ccache to reduce successive build times (use 3.2.5+ to avoid spurious warnings)
        curl -L "https://codeload.github.com/ccache/ccache/tar.gz/v3.2.5" | tar xvz && cd ccache-*