Escape new lines for TEXT->HTML conversions

[caronc]

Description:

Related issue (if applicable): #616

Bugfix introduced in Apprise v0.9.9 where \n is no longer correctly escaped when converting from TEXT -> HTML as a result of past code re-factoring.

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 as follows:
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@/616-text-to-html-crlf-fix

# Test out the changes with the following command:
apprise -t "Test Title" -b "Test Message" \
  "<apprise url>"

[codecov-commenter]

Codecov Report

Merging #617 (79f0db3) into master (1519e98) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #617   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          112       112           
  Lines        14416     14416           
  Branches      2725      2725           
=========================================
  Hits         14416     14416           

Impacted Files	Coverage Δ
apprise/URLBase.py	100.00% <100.00%> (ø)
apprise/conversion.py	100.00% <100.00%> (ø)

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