MC-89: MagentoAttributeHelper and Normalizer refactored, renamed and moved

MagentoAttributeHelper moved from Helper to Normalizer
'' renamed LabelDictionary
'' all static to constant and remove getter setter
Normalizers use LabelDict without injected it, as static
Re-add travis file
Merge pull request #295 from akeneo/MC-89

MC-89: MagentoAttributeHelper and Normalizer refactored, renamed and moved