Incorporate most changes from @weilawei. Enforce PEP8 everywhere.
General improvements.
Fix dict access of OP results. OP info now goes to info file.
Fix DC sweeps.
ISource and VSource have a complex ac_value. Keep the name alpha for now.
Transfer functions are results instances too.
Bugfix (ac_value).
Convert ext_nX keywords to nX: they are ext nodes, but no need to continously remind the user about that.
Results are now matplotlib-friendly arrays. No transposeing.
Update test results.
Bugfix.
Version bump.
Merge pull request #13 from ahkab/massive_cleanup

Clean-ups and several bug fixes.