Updated documentation and README to help with controlling Apprise Ver

[caronc]

Description:

Just a small push that updates the documentation for users who want to pull/check out a different version of Apprise outside of the stable version which is always the default.

Checklist

• [x] The code change is tested and works locally.
• [x] There is no commented out code in this PR.
• [x] No lint errors (use flake8)
• [ ] Tests added

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -0.07% :warning:

Comparison is base (669619e) 94.97% compared to head (8f12060) 94.90%. Report is 1 commits behind head on master.

:exclamation: Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the Github App Integration for your organization. Read more.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #132 +/- ## ========================================== - Coverage 94.97% 94.90% -0.07% ========================================== Files 15 15 Lines 1433 1434 +1 ========================================== Hits 1361 1361 - Misses 72 73 +1 ``` [see 1 file with indirect coverage changes](https://app.codecov.io/gh/caronc/apprise-api/pull/132/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Chris+Caron)

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.