Use nvm instead of travis node_js key

This fixes issues on container builds that would always use
node 6 even when 4 was specified.

Author: TheMarex

.travis.yml

@@ -7,8 +7,9 @@ git:
 sudo: required
 dist: trusty
 
-nodejs:
+node_js:
     - "4"
+    - "6"
 
 notifications:
   email: false
@@ -37,6 +38,7 @@ env:
    - CCACHE_VERSION=3.3.1
    - CMAKE_VERSION=3.7.2
    - MASON="$(pwd)/scripts/mason.sh"
+   - NODE="4"
 
 matrix:
   fast_finish: true
@@ -142,7 +144,6 @@ matrix:
           sources: ['ubuntu-toolchain-r-test']
           packages: ['libstdc++-5-dev']
       env: CLANG_VERSION='4.0.0' BUILD_TYPE='Release' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4
-      nodejs: "4"
       install:
         - pushd ${OSRM_BUILD_DIR}
         - |
@@ -166,7 +167,6 @@ matrix:
           sources: ['ubuntu-toolchain-r-test']
           packages: ['libstdc++-5-dev']
       env: CLANG_VERSION='4.0.0' BUILD_TYPE='Debug' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4
-      nodejs: "4"
       install:
         - pushd ${OSRM_BUILD_DIR}
         - |
@@ -189,8 +189,7 @@ matrix:
         apt:
           sources: ['ubuntu-toolchain-r-test']
           packages: ['libstdc++-5-dev']
-      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Release' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4
-      nodejs: "6"
+      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Release' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4 NODE="6"
       install:
         - pushd ${OSRM_BUILD_DIR}
         - |
@@ -213,8 +212,7 @@ matrix:
         apt:
           sources: ['ubuntu-toolchain-r-test']
           packages: ['libstdc++-5-dev']
-      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Debug' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4
-      nodejs: "6"
+      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Debug' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4 NODE="6"
       install:
         - pushd ${OSRM_BUILD_DIR}
         - |
@@ -231,6 +229,9 @@ matrix:
         - ./scripts/travis/publish.sh
 
 before_install:
+  - source $NVM_DIR/nvm.sh
+  - nvm use $NODE
+  - node --version
   - if [[ ! -z $TARGET_ARCH ]] ; then source ./scripts/travis/before_install.$TARGET_ARCH.sh ; fi
   - |
     if [[ -z $JOBS ]]; then