Unix build instructions

Added actual instructions rather than telling people to go read about where to find the instructions to read. Note that simple Windows instructions should be added as well.

INSTALL

@@ -33,13 +33,7 @@ CMake is the preferred build system for Assimp. The minimum required version
 is 2.6. If you don't have it yet, downloads for CMake can be found on
 http://www.cmake.org/. 
 
-Building Assimp with CMake is 'business as usual' if you've used CMake
-before. All steps can be done either on the command line / shell or
-by using the CMake GUI tool, the choice is up to you. 
-
-First, invoke CMake to generate build files for a particular
-toolchain (for standard GNU makefiles: cmake -G 'Unix Makefiles').
-Afterwards, use the generated build files to perform the actual
-build. 
-
+For Unix:
 
+1. cmake -G 'Unix Makefiles'
+2. make