Mod CONTRIBUTING to accept Github pull requests.
Unify version numbers for Clownfish and CFC.

Since both Clownfish and CFC will be released together in a single
Apache package, unify their version numbers.
Provide version numbers in all .pm files.
Add CFC CPAN prereqs, but avoid warning.

Reversing the logic (adding then conditionally deleting rather than
conditionally adding) means that the CPAN dist will generate a META.json
with the proper prereqs.
Adapt Lucy's update_version tool for Clownfish.
Udpate version to 0.4.0.
Use specific X.Y.Z version in Build.PL.

Otherwise, if we take it from CFC.pm the dist will be named
Clownfish-CFC-X.YYYZZZ.tar.gz when we want Clownfish-CFC-X.Y.Z.
Add CHANGES.
Remove extraneous material from LICENSE.

*   utf8proc
*   Snowball
*   US Constitution
Fix branding in INSTALL and README.

Use "Apache Clownfish" first, and use it as an adjective per trademark
guidelines.
Update release date in CHANGES.
Copy and adapt release_commands.pl from Lucy.
Remove support for void* return types

Assuming that a void pointer is a reference SV is fragile. The intention
of the mapping was to support bindings for the To_Host method. But
calling To_Host from the host language would simply return an identical
object, so I can't see a need to bind this method.
Function parameter and return type check

Move parameter and return type check from a static function in
CFCPerlClass to CFCPerlSub. Allow types which are either objects or
primitives.
Separate test whether to create method bindings

Move the code that checks whether bindings for a method should be
generated to a separate function.
Consolidate invalid callback check

Use the same function to check for invalid callbacks as for method
XSUBs.

Ultimately, we need a mechanism to disable the autogeneration of XSUBs
and callbacks separately. For now, it seems safer to keep callbacks for
excluded methods.