fixed tanh derivative
fixed normalization: takes maximum from absolute values
fixed regression charts

All working examples:
https://www.evernote.com/shard/s469/sh/96ce7ef9-2ce8-499e-98b6-5574de06f639/8b9869621b33b9ac18992854b1488052
Merge pull request #5 from pawelwieladek/feature/tanh-normalization

fixed tanh derivative