Install peerDependencies conditionally

Author: CaptEmulation

.travis.yml

@@ -6,8 +6,9 @@ before_install:
   - export DISPLAY=:99.0
   - sh -e /etc/init.d/xvfb start
 install:
+  # Install peerDependencies on > npm3
   # When all dependencies declare bitcore-lib as a peerDependency this can be bumped up, but this matches the current ecosystem version expected by dependencies
-  - npm install [email protected]
+  - if [ $(npm --version | sed 's/\..*//g') -ge 3 ]; then npm install [email protected]; fi
   - npm install
 after_script:
   - gulp coveralls