admin: fix Travis CI by using system Python

Squashed commit of the following:

commit 3a44301dac8de0fb72f89b4ed68050ea9cf9f7dc
Author: John Harrison <john@bloomonkey.co.uk>
Date:   Tue May 6 21:35:23 2014 +0100

    use Ubuntu system Python2.7

commit dd798ded36d2c34dd9fa110acee899d72662a186
Author: John Harrison <john@bloomonkey.co.uk>
Date:   Mon May 5 22:43:00 2014 +0100

    Revert "use ubuntu Python2.7 in tox"

    This reverts commit 99db139a379b119b49daf5d61c896aad9f1c2173.

    [ci skip]

commit c50f71d20dddfba35e627ccadef5a9d2b84099c5
Author: John Harrison <john@bloomonkey.co.uk>
Date:   Mon May 5 22:40:12 2014 +0100

    modify Travis CI config to not use tox"

commit f9a51b5957b9568d6080927baf1b631d25c77362
Author: John Harrison <john@bloomonkey.co.uk>
Date:   Mon May 5 22:26:28 2014 +0100

    fix typo in Travis CI config

commit 1517859f00437c63ac66fcaf8eeb34822967054a
Author: John Harrison <john@bloomonkey.co.uk>
Date:   Mon May 5 22:23:12 2014 +0100

    another attempt at finding pip downloaded bsddb3

commit aa35fa59444cc7bb2ad8e49b591e042db237a4d8
Author: John Harrison <john@bloomonkey.co.uk>
Date:   Mon May 5 21:48:26 2014 +0100

    workaround install of bsddb3 in Travis CI

commit 206872fbfdfbe6bd37d71f3ca84f16fd0dbf1464
Author: John Harrison <john@bloomonkey.co.uk>
Date:   Mon May 5 21:35:50 2014 +0100

    Revert "fix typo in Travis CI config"

    This reverts commit 948526c6a041cec42ba427c7ae8efdea9a43ea46.

commit 948526c6a041cec42ba427c7ae8efdea9a43ea46
Author: John Harrison <john@bloomonkey.co.uk>
Date:   Mon May 5 21:28:28 2014 +0100

    fix typo in Travis CI config

commit 4fd8c4341e6c2897c5616c7f2b34816e4f8822fe
Author: John Harrison <john@bloomonkey.co.uk>
Date:   Mon May 5 21:25:26 2014 +0100

    workaround install of bsddb3 in Travis CI

commit 99db139a379b119b49daf5d61c896aad9f1c2173
Author: John Harrison <john.harrison@liv.ac.uk>
Date:   Fri May 2 16:39:38 2014 +0100

    use ubuntu Python2.7 in tox

commit 12abd3c7d170eb596f3cadf6581be69a7ae6d8b9
Author: John Harrison <john.harrison@liv.ac.uk>
Date:   Fri May 2 14:24:35 2014 +0100

    modify Travis CI config to use tox

commit ac474df288f8fb74349904ca9722962f8833200b
Author: John Harrison <john.harrison@liv.ac.uk>
Date:   Fri May 2 14:21:41 2014 +0100

    add config for testing with tox

    [ci skip]

commit 80f4e8ce125e8e9457d9b263d02c16fb27bfe8e9
Author: John Harrison <john.harrison@liv.ac.uk>
Date:   Thu May 1 16:25:01 2014 +0100

    admin: further testing of Travis-CI config

commit 8fa0e9e12a43a84f6199143836f2f3e86aafe728
Author: John Harrison <john.harrison@liv.ac.uk>
Date:   Thu May 1 16:17:16 2014 +0100

    admin: tweak Travis-CI config