merge overview page from user guide into quickstart and delete it

docs/src/quickstart/overview.rst

 Cython - an overview
 ====================
 
-[Cython]_ is a programming language based on Python, with extra syntax
-allowing for optional static type declarations. It aims to become a superset
-of the [Python]_ language which gives it high-level, object-oriented,
-functional, and dynamic programming.  The source code gets translated
-into optimized C/C++ code and compiled as Python extension modules.
-This allows for both very fast program execution and tight integration
-with external C libraries, while keeping up the high programmer
-productivity for which the Python language is well known.
+[Cython] is a programming language that makes writing C extensions
+for the Python language as easy as Python itself.  It aims to become
+a superset of the [Python]_ language which gives it high-level,
+object-oriented, functional, and dynamic programming.  Its main feature
+on top of these is support for optional static type declarations as
+part of the language.  The source code gets translated into optimized
+C/C++ code and compiled as Python extension modules.  This allows for
+both very fast program execution and tight integration with external C
+libraries, while keeping up the high programmer productivity for
+which the Python language is well known.
 
 The primary Python execution environment is commonly referred to as
 CPython, as it is written in C.  Other major implementations use Java
@@ -19,8 +21,8 @@ has, however, remained non trivial to write the necessary glue code in
 C, especially for programmers who are more fluent in a high-level
 language like Python than in a close-to-the-metal language like C.
 
-Originally based on the well-known Pyrex [Pyrex]_, the Cython project has
-approached this problem by means of a source code compiler that
+Originally based on the well-known Pyrex [Pyrex]_, the Cython project
+has approached this problem by means of a source code compiler that
 translates Python code to equivalent C code.  This code is executed
 within the CPython runtime environment, but at the speed of compiled C
 and with the ability to call directly into C libraries. 

docs/src/userguide/index.rst

@@ -6,7 +6,6 @@ Contents:
 .. toctree::
    :maxdepth: 2
 
-   overview
    tutorial
    language_basics
    extension_types

docs/src/userguide/overview.rst

-.. highlight:: cython
-
-.. _overview:
-
-********
-Overview
-********
-
-About Cython
-==============
-
-Cython is a language that makes writing C extensions for the Python language
-as easy as Python itself. Cython is based on the well-known `Pyrex
-<http://www.cosc.canterbury.ac.nz/greg.ewing/python/Pyrex/>`_ language by Greg Ewing,
-but supports more cutting edge functionality and optimizations [#]_. 
-The Cython language is very close to the Python language, but Cython
-additionally supports calling C functions and declaring C types on variables
-and class attributes. This allows the compiler to generate very efficient C
-code from Cython code.
-
-This makes Cython the ideal language for wrapping external C libraries,
-and for fast C modules that speed up the execution of Python code.  
-
-Future Plans
-============
-Cython is not finished. Substantial tasks remaining. See
-:ref:`cython-limitations` for a current list. 
-
-.. rubric:: Footnotes
-
-.. [#] For differences with Pyrex see :ref:`pyrex-differences`.
-