ABC flow (synthesis, mapping) supported

[allegroCoder]

• Building & testing ABC on Travis and AppVeyor (fixed #17 )
• Espresso related flow for synthesis of the Boolean equations removed. It is replaced with ABC.
• README file updated with instructions for installing ABC, and for running Scenco under all the OSes.
• Added support for area estimation, verilog file generation.
• All the test present in https://github.com/allegroCoder/graph-families added and tested.
• Formulae as an entity composed by a combination of three lists {input, output, equations}.
• Removed log file generated by SCENCO
• Temporary files remove safely in case of any undefined errors.

[snowleopard]

I added a bunch of comments above :)

The main issue is that for some reason you are changing a perfectly clear strongly typed API with some error-prone and obscure one, where parameters are stored in files? This is even worse than having String parameters everywhere. Please bring the nice API we had back!

[allegroCoder]

@snowleopard now you can have a look at the PR for merging. Please, let me know if you want me to modify anything else. I have modified Formula.hs quite a lot. All the functions in there are useful for loading and unloading formulae into SCENCO for the technology mapping process, none of them are exported to the external environment though (following the approach we discussed if I am not mistaken).