Asciigraf

This release includes a complete rewrite of the edge exploring algorithm.

The rewrite adds support for edges like:

-----n2
|
n1

Bugs fixed:

- one character vertical labels not detected

Adds support for some extra corner configurations that were not handled before:


1-|
|
2


1
|
|--2


1
|
---2

* Adds networkx 2.x support
* Implements release-from-tag functionality using travis ci