[TRAVIS] Remove no longer used .travis_before_install file.
[TRAVIS] Update nose to overcome regression in nose 1.2.1.
[TRAVIS] Add CI for Python 3.4.
Let EggBasketPluginManager handle egg distribution errors.

Previously, an incorrect egg in the plugin_path such as an
inconsistent egg name with the version of the package would
cause the plugin manager to fail.
The `on_broken_distribution` trait can now be set on the
plugin manager to handle errors such as VersionConflict in
the eggs in the plugin_path, in a similar way to how
plugin load errors can be handled by setting the
`on_broken_plugin` trait.