Test coverage could be improved

[alisonrclarke]

UI tests are currently minimal. Should ensure we test all cases for errors etc as part of selenium tests.

[sjmf]

Test coverage metrics for Python have been added and merged with the testcoverage branch and have been finalised in commit 1287d96.

We currently have 79% test coverage of Django/server-side code. Thought needs to be given to how we can measure client-side test coverage for the webdriver tests run with selenium.

PR #94 will add further test coverage when merged.