Fix FilesDataset arrays and TokenCountVectorizer numeric token (#363)

Implement Keep a changelog format

Update CHANGELOG with #238 fix

Prepare CHANGELOG for next fix release

Prepare CHANGELOG.md for next release

created tag 0.5.0

Update dependecies and coding style fixes

Update changelog and cs fixes

Prepare for next release

Increase iterations number in Backpropagation test (sometimes it fails)