Data2neo

New helper functions under `rel2graph.neo4j`

This release switches back to "id" instead of "elementId" for all cypher interactions, because its an order of magnitude faster.

Introduces merge and create functions in `relgraph.neo4j` and updates documentation to 1.0 api. Adds logo.

This release marks the first full release of the rel2graph library. Compared to previous versions it is now completely independent of the py2neo library and solely depends on the native neo4j python driver. Further to by consistent with neo4j and cypher, the RELATION keyword is renamed to RELATIONSHIP.

Fixed bug with pandasdataframeiterator: df was indexed by custom index, instead of index (.loc->.iloc)

Dynamic Buffer now regularly randomly checks whether small buffer sizes improve throughput. This is especially usefull for relations that can have a low throughput and non-linear performance behavior in comparison to buffer size.