Update INSTALL.md

INSTALL.md

@@ -4,11 +4,11 @@
 Make sure that you have the requirements needed. These are
 
 - Core
-  - Node.js >=0.8
-  - npm >=1.2.1 <2.0.0
+  - Node.js >=6.9.x
+  - yarn >=0.21.3
   - PostgreSQL >8.3.x, PostGIS >1.5.x
   - Redis >2.4.0 (http://www.redis.io)
-  - Mapnik 2.0.1, 2.0.2, 2.1.0, 2.2.0, 2.3.0. See [Installing Mapnik](https://github.com/CartoDB/Windshaft#installing-mapnik).
+  - Mapnik >3.x. See [Installing Mapnik](https://github.com/CartoDB/Windshaft#installing-mapnik).
   - Windshaft: check [Windshaft dependencies and installation notes](https://github.com/CartoDB/Windshaft#dependencies)
   - libcairo2-dev, libpango1.0-dev, libjpeg8-dev and libgif-dev for server side canvas support
 
@@ -43,11 +43,11 @@ psql -d template_postgis -c 'CREATE EXTENSION postgis;'
 To fetch and build all node-based dependencies, run:
 
 ```
-npm install
+yarn [install]
 ```
 
-Note that the ```npm install``` step will populate the node_modules/
+Note that the ```yarn``` step will populate the node_modules/
 directory with modules, some of which being compiled on demand. If you
 happen to have startup errors you may need to force rebuilding those
 modules. At any time just wipe out the node_modules/ directory and run
-```npm install``` again.
+```yarn``` again.