Add coveralls.io support

Squashed commit of the following:

commit 63c52179a10bf4327ba4220099066f48ca56696b
Merge: 7969231 0637100
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Thu Feb 20 17:08:00 2014 +0100

    Merge branch 'master' of github.com:ckan/ckanext-b2 into coveralls

commit 7969231c181d9421d518c56198d7ef434d3da4b2
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Thu Feb 20 12:57:41 2014 +0100

    Correct mistake in travis nosetests command

commit fe18168495b585a931a7c7ce30d942e65708f9ef
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Thu Feb 20 12:43:49 2014 +0100

    Correct mistake in nosetests command

commit 240f87b7b6f84ae89c921a8bc6198c382a407986
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Thu Feb 20 12:06:49 2014 +0100

    Include all Python files in coverage report

    Including files that are not imported by the tests. This works locally,
    let's see if it works on coveralls.

commit 6355f87bd38bf75353eb95cbf185d6a3213dad8c
Merge: 7c3a02b 75625f6
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Thu Feb 20 11:04:11 2014 +0100

    Merge branch 'master' of github.com:ckan/ckanext-b2 into coveralls

    Conflicts:
    	.travis.yml

commit 7c3a02b64b26408aff8ff9b45ad3b1ada52d1989
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Wed Feb 19 21:43:23 2014 +0100

    Try to make coverage report include all Python files

    Not sure if it will understand this pattern syntax

commit 04938c087c0d6bfd539a5bf09c822b88cba8c251
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Wed Feb 19 11:51:20 2014 +0100

    Add Coveralls bade to README

commit 78c11b80d688e1ade2d01db41e530c469f1461c6
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Wed Feb 19 11:43:50 2014 +0100

    Omit */python2.7/* from coverage report

commit c971c876a03d2d95e2e94270c052ff37ab8a7b2f
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Wed Feb 19 11:41:59 2014 +0100

    Put ignore ckan back in coveragerc

commit 227b41ab3852554405f57d2d7c9b8b9e46cbf209
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Wed Feb 19 11:28:37 2014 +0100

    Try to omit site-packages stuff from coverage report

commit 75443bf212d5c1530c19c06e9b9207da9db0ec91
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Wed Feb 19 11:17:04 2014 +0100

    Do I really need the omit in coveragerc?

commit d910c488f35fc948695515ba736ae872229e5ef1
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Wed Feb 19 11:04:44 2014 +0100

    Try to omit ckan from coverage

commit 70e18aafabe0d058d9658dd9ed2cf7f46acc82c1
Author: Sean Hammond <seanhammond@lavabit.com>
Date:   Tue Feb 18 21:04:04 2014 +0100

    Trying to get coveralls working