numpy is also needed to build python API docs (#1253)

doc/sphinx/source/install.rst

@@ -153,8 +153,8 @@ The process documented here will work on CentOS 7.4.
       $ wget https://cmake.org/files/v3.4/cmake-3.4.3.tar.gz      
       $ tar -xzvf cmake-3.4.3.tar.gz
       $ cd cmake-3.4.3
-      $ ./bootstrap
-      $ make && sudo make install  
+      $ ./bootstrap --system-curl --prefix=~/cmake
+      $ make && make install     
 
 #. Clone the `NervanaSystems` ``ngraph`` repo via HTTPS and use Cmake 3.4.3 to 
    build nGraph Libraries to ``~/ngraph_dist``. 
@@ -164,7 +164,7 @@ The process documented here will work on CentOS 7.4.
       $ cd /opt/libraries 
       $ git clone https://github.com/NervanaSystems/ngraph.git
       $ cd ngraph && mkdir build && cd build
-      $ cmake ../ -DCMAKE_INSTALL_PREFIX=~/ngraph_dist  
+      $ ~/cmake/bin/cmake .. -DCMAKE_INSTALL_PREFIX=~/ngraph_dist  
       $ make && sudo make install 
 
 

doc/sphinx/source/project/doc-contributor-README.rst

@@ -117,15 +117,16 @@ Right now the minimal version of Sphinx needed to build the documentation is
 Sphinx v. 1.6.5.  This can be installed with :command:`pip3`, either to a virtual 
 environment, or to your base system if you plan to contribute much core code or
 documentation. For C++ API docs that contain inheritance diagrams and collaboration
-diagrams which are helpful for framework integratons, or for building bridge code, 
-be sure you have a system capable of running `doxygen`_.   
+diagrams which are helpful for framework integratons, building bridge code, or 
+creating a backend UI for your own custom framework, be sure you have a system 
+capable of running `doxygen`_.   
 
 To build documentation locally, run: 
 
    .. code-block:: console
 
       $ pip3 install [-I] Sphinx==1.6.5 [--user] 
-      $ pip3 install [-I] breathe [--user]
+      $ pip3 install [-I] breathe numpy [--user]
       $ cd doc/sphinx/
       $ make html
       $ cd build/html
@@ -139,7 +140,7 @@ To build documentation in a python3 virtualenv, run:
 
       $ python3 -m venv py3doc
       $ . py3doc/bin/activate
-      (py3doc)$ pip install sphinx breathe
+      (py3doc)$ pip install sphinx breathe numpy
       (py3doc)$ cd doc/sphinx
       (py3doc)$ make html
       (py3doc)$ cd build/html