Attempt at fixing errors on travis and appveyor

.travis.yml

@@ -108,6 +108,11 @@ before_install:
       brew install doxygen fftw;
       sudo easy_install pytest;
     fi
+  - if [[ "${TRAVIS_OS_NAME}" == "linux" ]]; then
+      CMAKE_URL="https://cmake.org/files/v3.7/cmake-3.7.2-Linux-x86_64.tar.gz"
+      mkdir cmake && travis_retry wget --no-check-certificate --quiet -O - ${CMAKE_URL} | tar --strip-components=1 -xz -C cmake
+      export PATH=${DEPS_DIR}/cmake/bin:${PATH}
+    fi
   - if [[ "$OPENCL" == "true" ]]; then
       wget http://s3.amazonaws.com/omnia-ci/AMD-APP-SDKInstaller-v3.0.130.135-GA-linux64.tar.bz2;
       tar -xjf AMD-APP-SDK*.tar.bz2;

appveyor.yml

-os: Windows Server 2012 R2
+os: Visual Studio 2015
 shallow_clone: true
 install:
 
-# Setup shell for VS2010, x64, release mode
+# Setup shell for VS2015, x64, release mode
   - >
     "%ProgramFiles%\Microsoft SDKs\Windows\v7.1\Bin\SetEnv.cmd" /x64 /release
 # Set path to python, git-bash tools.

docs-source/usersguide/library.rst

@@ -404,7 +404,7 @@ version of Visual Studio.
 Install CMake
 =============
 
-CMake is the build system used for OpenMM.  You must install CMake version 2.8
+CMake is the build system used for OpenMM.  You must install CMake version 3.1
 or higher before attempting to build OpenMM from source.  You can get CMake from
 http://www.cmake.org/.  If you choose to build CMake from source on Linux, make
 sure you have the curses library installed beforehand, so that you will be able
@@ -509,7 +509,7 @@ Windows
 
 On Windows, perform the following steps:
 
-#. Click Start->All Programs->CMake 2.8->CMake
+#. Click Start->All Programs->CMake 3.1->CMake
 #. In the box labeled "Where is the source code:" browse to OpenMM src directory
    (containing top CMakeLists.txt)
 #. In the box labeled "Where to build the binaries" browse to your build_openmm