[proposal_test.py] - test_propose function now also
                     check variance, not only mean
                   - added comments:
                     "test if value for rng can be omitted"
[proposal.py]  - made some variables private by
                 renaming them var --> _var
               - _inherit_docstring decorator
                  introduced (see also: tools.py)

[_tools.py]    - private helper functions introduced
               - _inherit_docstring decorator
                 introduced (see also: proposal.py)

[version.py]   - renamed to _version.py
[proposal.py]  - merged classes ProposalDensity and AdaptiveProposal
                 into the single class ProposalDensity

[__init__.py]  - modified the imports to be module level imports
added new modules: indicator_factory, markov_chain
moved all work to the new submodule "mcprerun"
made all relative imports explicitly relative (from . import ...)

tested with nosetests for python 2.7 and for python 3

Signed-off-by: Stephan Jahn <gu92biv@mytum.de>
[_tools.py]            corrected typo in docstrings
[indicator_factory.py] clarified docstings
[markov_chain.py]      clarified docstings
[_tools.py]   - added function "_add_to_docstring"
[proposal.py] - using the new _tool: better discrimination of
                requirements on ``rng`` according to the classes
              - removed "adapt" (will be moved to markov_chain)
[markov_chain.py] introduced class "AdaptiveMarkovChain"
introduced private submodule _tools
_tools.py moved _tools/_doc.py
moved class _Chain from [mcprerun/markov_chain.py] to [_tools/_chain.py]

introduced class _hist in [_tools/_chain.py] for saving the history
of _chain instances
included memory-preallocation for chain history
[markov_chain_test.py] included more detailed test about preallocated memory
[markov_chain] Update doc, add references
[indicator_factory] Remove default args