Update JIDT, fix formatting and pylint issues

Add MPI-support and Python estimators

Allow a maximum lag of 1

Allow a maximum lag of 1. This failed before because tau was required to
be at least 1 and the max. lag was required to be strictly larger than
tau.

Update sphinx documentation

Merge branch 'develop'

Add units of returned values.

Fixes #51.

Fix networkx export of nodes without links

Fix networkx export of nodes without links. The creation of the DiGraph
object was done by interating over links in the results. This did not
pick up nodes with no inferred links.

Fixes #50.

Fix surrogates for sequential maximum statistics

Fix surrogates for sequential maximum statistics. In the old version,
one candidate was missing from the conditioning set when generating
surrogates for sequential max stats. Now the surrogates for each
canditate are created by using a conditioning set that consists of all
selected source and target variables (source variables only for MI
calculation), excluding the candidate that is currently tested.

Add unit test for bivariate sequential max stats.

Peer reviewed and accepted for publication in JOSS

JOSS submission