Restructure to put DataFrame code in a separate package

Squashed commit of the following:

commit 2dec0687564143e3e62ab737179b065f42b8bd65
Author: Sharif Olorin <sio@tesser.org>
Date:   Wed Jan 15 20:46:41 2014 +1100

    Formatting

commit 3025e0d279d66a6a26f68c200fc692360d93e797
Author: Sharif Olorin <sio@tesser.org>
Date:   Wed Jan 15 20:44:05 2014 +1100

    Package comment

commit 165e81424993b93a26ac651641644422f89ef49f
Author: Sharif Olorin <sio@tesser.org>
Date:   Wed Jan 15 20:37:12 2014 +1100

    Restructure to put DataFrame code in a separate package

    It makes more sense for them to be separate at this point, given that
    this is the semiofficial vaultaire DataFrame implementation in Go
    anyway, and we'll want to be able to `go get` it separately.