Merge in work on backwards move generation

Squashed commit of the following:

commit 04f038167dd868036e684651d741d01a205b333d
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Fri Nov 8 08:14:30 2013 -0600

    Seems like a nice test to add

commit c1344c423b10df6d49204013639ba64b1b1abe1d
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Fri Nov 8 08:09:08 2013 -0600

    Test was failing, fixed bug in filter

commit ec41c5d68334e0e5d45fe7096e54c17de9e019cf
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 22:40:59 2013 -0600

    Filter by piece set for unpromotions too

    One of the simple-check tests is crashing for large sizes though o_O

commit f38511ee3211a86b37a12bb3eba67a4ebd6dd389
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 19:38:34 2013 -0600

    Filtering backward moves by piece set now

commit 8b8923c7629d65ed09bb670b1784528e5f24f1a7
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 19:34:58 2013 -0600

    Moves function for returning the captured piece

commit 3c03dc2aafbeb984d8f80a3cde0be9f72a83d899
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 16:21:58 2013 -0600

    Add a test that might not be contributing very much

commit 886fd4f7b3aaf875bb94197855f9ca7f32167100
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 15:23:11 2013 -0600

    Set en-passant square when moving backwards

commit 1139dc99efc250ab87aae816b9f4df90f91db2b6
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 15:16:24 2013 -0600

    EP and castling unmoves implemented

commit 868f224076bc97f63154b1fe11ea233d2eca0532
Merge: 50d114f 63276b4
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 09:07:45 2013 -0600

    Merge branch 'master' into backwards

    Conflicts:
    	src/com/gfredericks/chess/position.clj
    	test/com/gfredericks/chess/generators.clj

commit 50d114f0b367b83d7ff6d10c74ab0cf8795592e9
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 08:31:58 2013 -0600

    Fix serialization of positions with en-passant square

commit 542f7f2c485586e90bc33d0f02cfcedd75fc4f33
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 08:06:48 2013 -0600

    Fix bug in castling logic

commit d4a2bdec74225aa473d66bacd05009303d046459
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 07:50:52 2013 -0600

    Check roundtripping on positions reachable from the initial

commit e04fcd5b55ea886ab582eb8e4292812091b57117
Merge: 41f6197 f395856
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 07:33:18 2013 -0600

    Merge branch 'master' into backwards

commit 41f619770939bf992c0cfb36055d970b0546934b
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Thu Nov 7 07:30:57 2013 -0600

    Nominally generating castling/EP positions, but still passing

commit 90345a545d621eb5f8bc46fe0f00bbb80d1ae87a
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Tue Nov 5 22:13:13 2013 -0600

    The test in the other direction is mostly passing. Need better tests I guess.

commit 499dd1646b731eef83cf733e38fba483be302fb7
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Tue Nov 5 21:23:20 2013 -0600

    Current tests passing; need more properties

commit 56d7bfb58f74be12c1d741726c0cf97f5adeb63e
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Tue Nov 5 20:31:33 2013 -0600

    save game

commit 2da4d4ef20276850d4509167f96ed012557ed9dd
Author: Gary Fredericks <fredericksgary@gmail.com>
Date:   Tue Nov 5 11:26:00 2013 -0600

    Backwards WIP
Version bump