swap nvm for mason node

scripts/install_node.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+set -e
+set -o pipefail
+
+mason install node $NODE_VERSION
+export PATH="`mason prefix node $NODE_VERSION`/bin":"$PATH"
+node --version
+npm --version

scripts/install_nvm.sh

@@ -1,11 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-set -o pipefail
-
-git clone git@github.com:creationix/nvm.git ../.nvm
-source ../.nvm/nvm.sh
-nvm install $NODE_NVM_VERSION
-nvm use $NODE_NVM_VERSION
-node --version
-npm --version