REF: use relative imports instead of absolute imports.
BUG: fix one broken relative import.
MAINT: let's add 2.5 as well.
MAINT: add 2.5 in travis-ci.
BUG: fix python 2.5.
Revert "BUG: fix python 2.5."

This reverts commit 3ed7eb4dc9599c27eaea868cb0863162b4eae51f.
Revert "MAINT: add 2.5 in travis-ci."

This reverts commit 717fc0bde626cfe92964a0cd4cb6d7eb69867145.
Revert "MAINT: let's add 2.5 as well."

This reverts commit 5a6dc5467a04666b7cfa2b00efa43c8147957804.
MAINT: ensure we always erase coverage results in tox.
Merge branch 'use_relative_imports'
ENH: group requirements for same package name together.
ENH: fix requirement round trip.
TST: add another test for provides/replaces.