Update README.md

README.md

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 ![alt text](https://raw.githubusercontent.com/eclipse/xacc/master/docs/assets/xacc-readme.jpg)
 
 ## Language and Hardware Independent Quantum Programming Framework
-XACC is an extensible compilation framework for hybrid quantum-classical computing architectures. It provides extensible language frontend and hardware backend compilation components glued together via a novel quantum intermediate representation. XACC currently supports quantum-classical programming and enables the execution of quantum kernels on IBM, Rigetti, and D-Wave QPUs, as well as a number of quantum computer simulators.
+XACC is an extensible compilation framework for hybrid quantum-classical computing architectures. 
+It provides extensible language frontend and hardware backend compilation components glued together 
+via a novel quantum intermediate representation. XACC currently supports quantum-classical programming 
+and enables the execution of quantum kernels on IBM, Rigetti, and D-Wave QPUs, as well as a number 
+of quantum computer simulators.
 
 Documentation
 -------------
@@ -15,16 +19,35 @@ Documentation
 
 Build from Source
 -----------------
-Ensure that you have installed CMake 3.2+, a C++11 compliant compiler (GCC 5+, Clang 3.8+), and OpenSSL development libraries (see [prerequisites](http://xacc.readthedocs.io/en/latest/install.html#pre-requisites)).
+Ensure that you have installed CMake 3.2+, a C++11 compliant compiler (GCC 5+, Clang 3.8+), and 
+CURL development headers and libraries with OpenSSL support 
+(see [prerequisites](http://xacc.readthedocs.io/en/latest/install.html#pre-requisites)). 
+
+Optional dependencies include BLAS and LAPACK development libraries (for various simulators), 
+Python 3 development headers and library (for the Python API), and Libunwind (for stack trace printing).
 
 Clone the repository recursively, configure with `cmake` and build with `make`
 ```bash
 $ git clone --recursive https://github.com/eclipse/xacc
 $ cd xacc && mkdir build && cd build
-$ cmake ..
+[default] 
+$ cmake .. 
+[with python api] 
+$ cmake .. -DPYTHON_INCLUDE_DIR=/path/to/python/headers
+[with tests]
+$ cmake .. -DXACC_BUILD_TESTS=TRUE 
+[or any combination of the above]
+$ cmake .. -DPYTHON_INCLUDE_DIR=/path/to/python/headers -DXACC_BUILD_TESTS=TRUE 
+[now build xacc]
 $ make install
+[if you built with tests]
+$ ctest
+```
+Your installation will be in `$HOME/.xacc`. If you built with the Python API, be sure to update your `PYTHONPATH` 
+environment variable to point to the installation:
+```bash
+$ export PYTHONPATH=$PYTHONPATH:$HOME/.xacc
 ```
-Your install will be in `$HOME/.xacc`. To change the install location, pass `-DCMAKE_INSTALL_PREFIX=/path/to/custom/install` to `cmake`. To build the Python API (**recommended)**, pass `-DPYTHON_INCLUDE_DIR=/usr/include/python3.5` (or wherever your Python.h is located) to `cmake`.
 
 Questions, Bug Reporting, and Issue Tracking
 --------------------------------------------