Update .travis.yml

running travis on 3.4
Handle %-chars in invalid lines correctly

The use of string formatting for inserting the line number doesn't work
well if the line itself contains percents. This patch avoids the use of
directly formatting the text, and also cleans up some inconsistencies
(``at line "%s"`` vs `` at line %s``).
Merge pull request #66 from untitaker/string_formatting

Handle %-chars in invalid lines correctly
Fix unhelpful error message when nesting invalid.

See https://github.com/geier/khal/issues/105
Merge pull request #67 from untitaker/no_parent

Fix unhelpful error message when nesting invalid.
tagging 5.0.6; fixes #59
Merge branch 'release' of github.com:DiffSK/configobj into release