Try bumping Travis Ubuntu version.

Former-commit-id: cde4f555fae3f3756d74314439dc2fa426bb6043

.gitmodules

@@ -1,8 +1,8 @@
 [submodule "external/nanogui"]
 	path = external/nanogui
-url=https://github.com/libigl/nanogui.git
-        fetchRecursiveSubmodules = true
-        ignore = dirty
+	url=https://github.com/libigl/nanogui.git
+	fetchRecursiveSubmodules = true
+	ignore = dirty
 [submodule "external/embree"]
 	path = external/embree
 	url = https://github.com/embree/embree.git

.travis.yml

@@ -1,6 +1,6 @@
 language: cpp
 sudo: false
-dist: precise
+dist: trusty
 matrix:
   include:
     - os: linux

shared/cmake/libigl.cmake

@@ -355,7 +355,7 @@ if(LIBIGL_WITH_OPENGL)
     target_link_libraries(igl_viewer ${IGL_SCOPE} igl_core glfw glew ${OPENGL_gl_LIBRARY})
     target_include_directories(igl_viewer SYSTEM ${IGL_SCOPE} ${OPENGL_INCLUDE_DIR})
     if(TARGET nanogui)
-      target_link_libraries(igl_viewer ${IGL_SCOPE} nanogui glew)
+      target_link_libraries(igl_viewer ${IGL_SCOPE} nanogui)
       target_compile_definitions(igl_viewer ${IGL_SCOPE} -DIGL_VIEWER_WITH_NANOGUI)
     endif()
   endif()