lib/diffs: mark trailing tabs similar to trailing spaces So far, spaces have not been marked up, but trailing spaces are followed by '<i></i>' (newline symbol). Tabs have been marked up as '<u>\t</u>' (underlined with icon), but trailing tabs didn't get the same "trailing whitespace" markup as trailing spaces got. Fix this unfairness by handling trailing tabs explicitly as '<u>\t</u><i></i>' so they get both kinds of markup.

[tox]
minversion = 1.8
envlist = py27-pytest

[testenv]
setenv =
    PYTHONHASHSEED = 0
deps =
    -r{toxinidir}/dev_requirements.txt
    python-ldap
    python-pam
commands =
    pytest: py.test {posargs}