Added program specific configurations in config.yaml under puudot
and added key for verbose mode. Currently verbose mode prints
'dot' information when running the program.
Refactored puudot.py and graph.py in order to allow easier
addition of output formats.
Hidden node was removed from a block to reduce empty space.
Link from previous level is connected to the node in the middle
(or the first of two middle nodes when even number of nodes).
Added ranksep in config to increase vertical space.
Restructured data to support block and node level links.
Added hidden nodes and edges in blocks to improve link
visualization.
Introduced support for configuring dot file parameters with
a config file.
