Fix installation instruction for ubuntu 14.04 (#805)

* fix installation instruction for ubuntu 14.04

* upgrade cmake requirements

* fix

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.4)
 
 project(ray)
 

doc/source/install-on-ubuntu.rst

@@ -32,6 +32,9 @@ To build Ray, first install the following dependencies. We recommend using
   sudo apt-get install python-dev  # For Python 2.
   sudo apt-get install python3-dev  # For Python 3.
 
+  # If you are on Ubuntu 14.04, you need the following.
+  pip install cmake
+
   pip install numpy cloudpickle funcsigs click colorama psutil redis flatbuffers
 
 

src/common/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.4)
 
 project(common)
 

src/common/redis_module/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.4)
 
 project(ray_redis_module)
 

src/global_scheduler/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.4)
 
 project(global_scheduler)
 

src/local_scheduler/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.4)
 
 project(local_scheduler)
 

src/numbuf/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.4)
 
 project(numbuf)
 

src/plasma/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.4)
 
 project(plasma)