Update changelog and bump version.

Avoid using column aliases in the HAVING clause (not allowed by
PostgreSQL).

Update changelog, bump version, and change gem home page from
code.alexreisner.com to github.com.

This makes the tests Rails 3 compatible. Adding /core_ext is necessary
or we don't have access to the class_inheritable_reader method.

This less accurate SQLite-compatible implementation is activated
automatically if an SQLite database is being used.

method.

When calculating geographic center, convert from degrees to radians before computation, then back again before returning.

This reverts commit fc0b5ba9.