Squashed commit of the following:

commit 8ca4d6f759ee1d54d3e31cc0ed1f82858bc85fca
Author: Maxwell Krohn <themax@gmail.com>
Date:   Thu Oct 9 21:38:38 2014 -0400

    Close #13

    Make simple leveldb []byte cache layer.  We might have to build
    something on top of it that does json serialization/deserialization.

commit 9d42ddc5331bbbca3e94e3abb91a2177a7aac055
Author: Maxwell Krohn <themax@gmail.com>
Date:   Thu Oct 9 20:34:46 2014 -0400

    a first stab at what our interface should be