Problem: nvm isn't installing properly on Travis

Solution: Rely on the nvm install script

Author: rgbkrk

.travis.yml

@@ -16,21 +16,13 @@ os:
 
 osx_image: xcode7.2
 
-matrix:
-  fast_finish: true
-  include:
-    - os: osx
-      env: NODE_VERSION="5" NVM_DIR=~/.nvm
-    - os: linux
-      env: NODE_VERSION="5"
-
 env:
- - ZMQ="4.0.5" SODIUM="1.0.5"
- - ZMQ="4.1.3" SODIUM="1.0.5"
+ - ZMQ="4.1.3" SODIUM="1.0.5" NODE_VERSION="5"
+ - ZMQ="4.1.3" SODIUM="1.0.5" NODE_VERSION="4"
 
 before_install:
- - git clone https://github.com/creationix/nvm.git ./.nvm
- - source ./.nvm/nvm.sh
+ - curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.30.2/install.sh | bash
+ - source ~/.nvm/nvm.sh
  - nvm install $NODE_VERSION
  - nvm use $NODE_VERSION
  - node --version