Pypyr

- If pypyr context can't create, create an empty pypyr Context to allow failure handler steps access to the pypyr Context even if empty - steps reasonably can expect a Context-like type input

- utils folder missing __init__.py. Added.

- wait_until_true had an unnecessary wait after the last loop attempt finished executing. Remedied.

- get_formatted_as_type previously would return True for all str -> bool conversions. Now 'True' will return `True`, and all other strings return `False` when casting to bool.

- wait_until_true decorator
- add pypyr utils _wait_until_true_. This allows you to decorate any given function with `wait_until_true(interval, max_attempts)` and it will execute that function on the specified intervals until max attempts reached, until the function returns true.
- add context get_formatted_as_type, to format string values AND return as a certain type that's not necessarily a string.

- add string substitution support to
- fetchjson
- fetchyaml
- fileformat
- fileformatjson
- fileformatyaml
- filereplace
- [sic] strings, for when you don't want to apply {formatting} to a string
- README help updates for substitutions