move PyPy porting doc page to userguide (not a tutorial), move early-binding page more to the front

--HG--
rename : docs/src/tutorial/pypy.rst => docs/src/userguide/pypy.rst

docs/src/tutorial/index.rst

@@ -13,7 +13,6 @@ Tutorials
    strings
    pure
    numpy
-   pypy
    readings
    related_work
    appendix

docs/src/userguide/index.rst

@@ -14,11 +14,12 @@ Contents:
    sharing_declarations
    external_C_code
    source_files_and_compilation
+   early_binding_for_speed
    wrapping_CPlusPlus
    fusedtypes
+   pypy
    limitations
    pyrex_differences
-   early_binding_for_speed
    memoryviews
    parallelism
    debugging