Enhancing Rasa: Recognizing lower case entities

• Try to use spacy_sklearn instead of tensorflow pipeline in 'rasa/nlu_config.yml'

• Like this:

language: "en"

pipeline:
- name: "nlp_spacy"
- name: "tokenizer_spacy"
- name: "intent_entity_featurizer_regex"
- name: "intent_featurizer_spacy"
- name: "ner_crf"
- name: "ner_synonyms"
- name: "intent_classifier_sklearn"