Messages

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- Minor bug fix and document changes.

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- Adds a SlackPost class, for the [chat.postMessage](https://api.slack.com/methods/chat.postMessage) API
- Changes TelegramBot.get_chat_id method to not be called by __init__, instead as a manual method to be called by the user as needed since Telegram's getUpdate method clears all entries after 24-hours.

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- Adds support for [Telegram Bot](https://core.telegram.org/bots/api#available-methods) messages
- Makes config.py and exceptions.py into private _*.py modules

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- Changes README.rst to README.md since now compatible on PyPI
- Reworked the \_utils.py module to be more functional and readable
- Removes the twilio sdk dependency and just uses the requests library

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- Enforces python \>= 3.5 for install
- Tweaks CLI args a bit for ease of use
- Adds more information to messages --help and docstrings for cli use

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- Adds a **-C**, **--configure** option to the CLI in order to
configure and create an entry in the config.json file for a specific
message type. That way default parameters and credentials can be
saved away for easier use later.