I'm abandoning streams in favor of iterators

Streams turned out to be not applicable: it is very hard to track/modify
traversal workflow with streams. After trying five different approaches
I was not satisfied with what I got. Using iterators will allow me to
compose traversing API, while also letting to easily track it.
Renamed VertexStream to VertexPipe
Restructured BasePipe
Updated verticsToEdgesStream
Renamed verticesToEdgesStream to verticesToEdgesPipe
Forgot to store graph structure in vertex pipe
Renamed class name for verticesToEdgesPipe
Converted edgesToVerticesStream into iterator
Renaming Streams to Pipes (since they are no longer streams)
Removed debugger; statement
Added reminder for future self
Converted VerticesToVerticesStream to iterator
Enabled graph of gods tests
Renamed file for vertices to vertices pipe
Renamed test file too
Added Path pipe to track pipelines
Renamed Streams to Pipes