Release notes for cubature code

The following are the main changes in each subsequent tagged release of the cubature code by Steven G. Johnson.

Version 1.0.4

Fix hang in hcubature for certain integrands (#14).

Version 1.0.3

Transferred files and documentation to Github.

Version 1.0.2

Fix memory leak in hcubature on BSD (and MacOS) systems. Thanks to Nicolas Tessore (@ntessore) for the bug report.

Version 1.0.1

cubature.h header now includes <stdlib.h>, to make sure size_t is defined

Version 1.0

Many API changes compared to pre-1.0 versions:
- rename adapt_integrate -> hcubature
- integrand now returns int to signal errors
- error_norm argument for vector-valued integrands
- maxeval and npt args are now size_t, not int
New pcubature routines for p-adaptive (Clenshaw-Curtis) integration.
Split test.c and some #include stuff from hcubature.c (to share with pcubature.c).