Add conda environment file for boost (helpful for Windows users). (#1239)

* Add conda environment file for boost (helpful for Windows users).

* Try to update Travis image for macOS.

.travis.yml

@@ -41,14 +41,17 @@ matrix:
     env:
     - MATRIX_EVAL="export CC=gcc-7 CXX=g++-7 CONFIG=Release PYTHON=python3 CMAKE_EXTRA='-DLIBIGL_EIGEN_VERSION=3.3.7'"
   - os: osx
+    osx_image: xcode10.2
     compiler: clang
     env:
     - MATRIX_EVAL="export CONFIG=Debug PYTHON=python3 LIBIGL_NUM_THREADS=1"
   - os: osx # same config like above but with -DLIBIGL_USE_STATIC_LIBRARY=OFF to test static and header-only builds
+    osx_image: xcode10.2
     compiler: clang
     env:
     - MATRIX_EVAL="export CONFIG=Debug PYTHON=python3 LIBIGL_NUM_THREADS=1 CMAKE_EXTRA='-DLIBIGL_USE_STATIC_LIBRARY=OFF'"
   - os: osx
+    osx_image: xcode10.2
     compiler: clang
     env:
     - MATRIX_EVAL="export CONFIG=Debug PYTHON=python3 LIBIGL_NUM_THREADS=1 CMAKE_EXTRA='-DLIBIGL_EIGEN_VERSION=3.3.7'""

cmake/libigl-cgal.yml

@@ -0,0 +1,8 @@
+# This is a conda environment that can be used to compile libigl with CGAL on Windows
+# Only boost is required to be installed on the system, CGAL is automatically downloaded
+# by CMake and is built with libigl.
+name: libigl-cgal
+channels:
+  - conda-forge
+dependencies:
+  - boost-cpp=1.65.0