BUG: fix --userpass when no username is entered.
MAINT: include functional test suite in travis-ci (and tox).
MAINT: don't run the functional test suite twice in travis-ci.
BUG: fix py2.6.
MAINT: tweak tox to not include coverage by default.
BUG: fix enpkg --userpass when creds are invalid.
TST: add functional test for 'enpkg requirement' with invalid auth.
ENH: test main_noexc instead of main in function tests.
ENH: tweak error message when auth fails.
Merge pull request #161 from enthought/fix_enstaller_auth_crash

Fix enstaller auth crash