allow `compat` to function as client for arakoon system tests

TODO: dirty reads
Merge branch 'master' into system_tests_1.7

* master:
  Add `replace` call
  Implement `collapse_tlog`
  Add support for `AssertExists` sequence steps
  Raise `NotConnectedError` instead of generic `RuntimeError`
  Add `__repr__` to `Request` and `Result`
  Implement actual `allow_dirty` support

Conflicts:
	pyrakoon/sequence.py
Fixup tests
Fixup 49ae1341e1d1e0e577484469fdf824f4e984ba97
Merge branch 'system_tests_1.7'

* system_tests_1.7:
  Fixup 49ae1341e1d1e0e577484469fdf824f4e984ba97
  Fixup tests
  allow `compat` to function as client for arakoon system tests