rocket.chat basic message structure fix

[caronc]

Description:

Related issue (if applicable): #406

This resolves an issue identified where basic Rocket.Chat messages would not work properly (however webhook worked fine).

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• No lint errors (use flake8)
• 100% test coverage

Testing

Anyone can help test this source code as follows:

# Create a virtual environment to work in
# This way you can just destroy it after when it's all over.
# The below will create a directory called apprise
python3 -m venv apprise

# Change into our new directory
cd apprise

# Activate our virtual environment
source bin/activate

# Install the branch
pip install git+https://github.com/caronc/apprise.git@406-rocket-chat-message-posting
# Give it a go:
# The syntax is like so:
# swap {values} accordingly:
apprise -t "Title" -b "Body" "rockets://{user}:{pass}@{host}"

[codecov-commenter]

Codecov Report

Merging #419 (ad91da5) into master (49af85b) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #419   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           94        94           
  Lines        11968     11972    +4     
  Branches      2012      2016    +4     
=========================================
+ Hits         11968     11972    +4     

Impacted Files	Coverage Δ
apprise/plugins/NotifyRocketChat.py	100.00% <100.00%> (ø)

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[hkpanchani]

@caronc
Thank you!!! Issue Resolved and can be pushed to release.
Can you share the procedure how can I update the existing apprise!?

[caronc]

@hkpanchani : The content is merged to the master now; it will be part of the next official build. But in the meantime, if you want to use it just install the master branch here (instead of what is in PyPi) into whatever environment it is you need it in:

# Install master branch:
pip install git+https://github.com/caronc/apprise.git