Change travis to build with and without libcapnp pre-installed

.travis.yml

@@ -6,18 +6,14 @@ python:
   - 3.3
   - pypy
 
+env:
+  - BUILD_CAPNP=true
+  - BUILD_CAPNP=
+
 compiler: gcc
 
 before_install:
-  - sudo apt-get install autoconf automake libtool autotools-dev
+  - buildutils/setup_travis.sh
-  - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
-  - sudo apt-get -qq update
-  - sudo apt-get -qq install g++-4.8 libstdc++-4.8-dev
-  - sudo update-alternatives --quiet --install /usr/bin/gcc  gcc  /usr/bin/gcc-4.8  60
-                                     --slave   /usr/bin/g++  g++  /usr/bin/g++-4.8
-                                     --slave   /usr/bin/gcov gcov /usr/bin/gcov-4.8
-  - sudo update-alternatives --quiet --set gcc /usr/bin/gcc-4.8
-  - wget https://github.com/kentonv/capnproto/archive/master.zip && unzip master.zip && cd capnproto-master/c++ && ./setup-autotools.sh && autoreconf -i && ./configure && make -j6 check && sudo make install && sudo ldconfig && cd ../..
   - pip install -U setuptools
   - pip install cython
   - pip install pytest

buildutils/setup_travis.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+sudo apt-get -qq update
+sudo apt-get -qq install g++-4.8 libstdc++-4.8-dev
+sudo update-alternatives --quiet --install /usr/bin/gcc  gcc  /usr/bin/gcc-4.8  60 --slave   /usr/bin/g++  g++  /usr/bin/g++-4.8 --slave   /usr/bin/gcov gcov /usr/bin/gcov-4.8
+sudo update-alternatives --quiet --set gcc /usr/bin/gcc-4.8
+
+if ! [ -z "${BUILD_CAPNP}" ]; then
+  sudo apt-get install autoconf automake libtool autotools-dev
+  wget https://github.com/kentonv/capnproto/archive/master.zip && unzip master.zip && cd capnproto-master/c++ && ./setup-autotools.sh && autoreconf -i && ./configure && make -j6 check && sudo make install && sudo ldconfig && cd ../..
+fi