DOC: Add notes about CUDA requirements for install

INSTALL.rst

@@ -2,19 +2,27 @@ Installing dependencies
 =======================
 To build and run TomoPy, you will need to install at least the dependencies
 listed in ``envs/{platform}-{version}.yml`` plus additional dependencies based
-on your platform. For example, installing requirements for building
+on your platform. For convenience, installing requirements for building
 the Python 3.6 version on Linux can be accomplished as follows::
 
     $ conda env create -f envs/linux-36.yml [-n ENVIRONMENT]
-
+    
+This will create a new conda environment named tomopy with the build
+dependencies. If you already have a conda environment named tomopy. Use the
+`-n` option to name it something else.
 
 Additional Windows Requirements
 -------------------------------
-The Windows VC++2017 compiler cannot be distributed through conda. You must
-install it using the Windows Build Tools installer. The conda package for this
-compiler merely searches for this compiler and links it to the conda
-environment into which it is installed.
+The Windows VC++2017 compiler cannot be distributed through conda. The conda
+package for this compiler creates link from the system provided compiler
+to the conda environment into which it is installed. Install VC++2017 using
+the Windows Build Tools installer; Visual Studio (the IDE) is not required
+to build TomoPy.
 
+Additional CUDA Requirements
+----------------------------
+The CUDA compiler cannot be distributed through conda. Building TomoPy with
+GPU features requires the CUDA Toolkit and NVCC.
 
 Building TomoPy
 ===============