Recreating Pull Request from @semuel in 2.4 Branch

https://github.com/movabletype/mt-plugin-reblog/pull/6 was merged into
the wrong branch, so the commit had to be reverted and reapplied to the
2.4 branch.
Bumped version number, removed dependency on Switch module

The version number was bumped from 2.3 to 2.4.  The Perl module Switch
is no longer required to run Reblog with newer versions of Perl 5.
Merge branch '2.4'