Different versions tests were update

* test_new_client test was updated
(with new elliptics.Session.add_remote logic)
* raises_elliptics_error matcher was added
(to be able to check exception type and exception code with the same
assert_that construct)
* relative import was corrected
(to make this import more explicit)
* usage of matches method was replaced with _matches method
('virtual' method _matches has to be used as it's implemented in
BaseMatcher class with NotImplementedError exception)
* defining for HasItems' attribute was moved to __init__
* unused imports were removed
Merge branch 'develop' into features/different-versions-tests-update
Merge pull request #31 - Different versions tests were update
Merge branch 'develop' into hotfixes
Merge pull request #32 - fix: for **setuptools must be installed to
install from a source distribution** pip error
Recovery dc tests were replaced with new version and some small changes:

* address family now passes explicitly
* test tags were corrected for recovery merge tests
* recovery merge tests were moved
(to prepare them for changes for recovery tests)
* a delay before running `dnet_recovery` was added
(for indexes synchronization)
* option name was corrected
fix: wrong type casting was corrected
Merge pull request #33 from features/replace-recovery-dc-tests

Recovery dc tests were replaced with new version and some small changes:
Merge branch 'develop' into hotfixes
fix: wiping out data before recovery tests