fix: removing restriction for replay file to have .json extension

[kakhaUrigashvili]

Addressing #347 and doing additional clean up

1. minor formatting change for some options descriptions
2. removing restriction for replay file to have .json extension
3. removed code to read/ write yml replay file, since it was not possible due to our validations.

test non exisiting file

ask dialog -r not-existing
[Error]: Failed to parse file: not-existing.
File not-existing not exists.

test non json file

ask dialog -r out
[Error]: Failed to parse file: out.
out: Unexpected string in JSON at position 166

test good file

ask dialog -r out

========================================================== Welcome to ASK Dialog ==========================================================
========================================= Replaying a multi turn conversation with Alexa from out =========================================
======================================== Alexa will then evaluate your input and give a response! =========================================

User  > open node crazy test
Alexa > Welcome, you can say Hello or Help. Which would you like to try?
User  > hello
Alexa > Hello World!
User  > .quit

================================================================ Goodbye! =================================================================

[RonWang]

LGTM