Add a README explaining how to build the library

README.rst

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+Axolotlpp
+=========
+
+An implementation of the axolotl ratchet written in C++11 and exposed as a C
+API.
+
+Building
+--------
+
+To build axolotlpp as a shared library run:
+
+.. code:: bash
+
+    ./build_shared_library.py
+
+To run the tests run:
+
+.. code:: bash
+
+   ./test.py
+
+
+To build the javascript bindings run:
+
+.. code:: bash
+
+    javascript/build.py
+
+Design
+------
+
+Axolotlpp is designed to be easy port to different platforms and to be easy
+to write bindings for.
+
+Error Handling
+~~~~~~~~~~~~~~
+
+All C functions in the API for axolotlpp return ``axolotl_error()`` on error.
+This makes it easy to check for error conditions within the language bindings.
+
+Random Numbers
+~~~~~~~~~~~~~~
+
+Axolotlpp doesn't generate random numbers itself. Instead the caller must
+provide the random data. This makes it easier to port the library to different
+platforms since the caller can use whatever cryptographic random number
+generator their platform provides.
+
+Memory
+~~~~~~
+
+Axolotlpp avoids calling malloc or allocating memory on the heap itself.
+Instead the library calculates how much memory will be needed to hold the
+output and the caller supplies a buffer of the appropriate size.
+
+Output Encoding
+~~~~~~~~~~~~~~~
+
+Binary output is encoded as base64 so that languages that prefer unicode
+strings will find it easier to handle the output.
+
+Dependencies
+~~~~~~~~~~~~
+
+Axolotlpp uses pure C implementations of the cryptographic primitives used by
+the ratchet. While this decreases the performance it makes it much easier
+to compile the library for different architectures.