Pusia-dev-tools

Fixed mistakes in README, changed `BackPathTrackerMixinView` to `BackPathTrackerMixin`.

Added new view mixins: `RequestFormKwargsMixin`, `GoogleReCAPTCHAMixin`, refactored `URLHistoryMixin` to `BackPathTrackerMixinView` .
Added form mixins: `RequestFormKwargsFormMixin`, `GoogleReCAPTCHAFormMixin` .
Added function: `get_random_string`.
Added custom exception: `NonAjaxRequestError`

HTML-parser refactored: added `HTMLBuilder`, new base parser 'BaseHTMLParser', `SingleElementHTMLParser`.
Fixed parsing issues: incorrect child parse. Added function `normalize_text` for replacing character groups in text strings.

Added mixins for views:
`AjaxRequiredMixin`, `URLHistoryMixin`, `MessageContextMixin`, `TitleContextMixin`, `JsonContextMixin`, `ExtendedViewMixin`, `ExtendedFormViewMixin` ;

Added views:
`ExtendedView`, `ExtendedFormView`, `ExtendedCreateView`, `ExtendedUpdateView`, `ExtendedDetailView`,
`ExtendedDeleteView`, `ExtendedTemplateView` .

added help functions:
format_datetime
camel_to_snake
safety_get_attribute
safety_parse_dict
get_class_from_path
get_class_from_settings

Start release