Drop 3.4 Support

[avylove]

Github dropped the Ubuntu 18.04 image we were using to test 3.4 and my distro doesn't have a package for it, so I think it's time to drop support.

If the query is correct, Blessed was only downloaded 509 times for Python 3.4 in the last 6 months.

This should fix the failing CI tests.

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (d404d8c) 95.38% compared to head (9bf91b6) 95.38%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #253 +/- ## ======================================= Coverage 95.38% 95.38% ======================================= Files 9 9 Lines 1018 1018 Branches 215 215 ======================================= Hits 971 971 Misses 43 43 Partials 4 4 ``` | [Impacted Files](https://app.codecov.io/gh/jquast/blessed/pull/253?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jeff+Quast) | Coverage Δ | | |---|---|---| | [blessed/formatters.py](https://app.codecov.io/gh/jquast/blessed/pull/253?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jeff+Quast#diff-Ymxlc3NlZC9mb3JtYXR0ZXJzLnB5) | `100.00% <ø> (ø)` | | | [blessed/terminal.py](https://app.codecov.io/gh/jquast/blessed/pull/253?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jeff+Quast#diff-Ymxlc3NlZC90ZXJtaW5hbC5weQ==) | `98.27% <ø> (ø)` | |

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[avylove]

Also switched the Codecov uploader to the GitHub Actions one because they dropped the Python one from PyPI.

[avylove]

Also needed to fix a Sphinx config issue and fix paths for tox.

[avylove]

@jquast I think this is ready. Should fix the CI tests

[jquast]

I suppose the code would still theoretically work with 3.4, we just can't test it, just to remind that python_requires can allow older versions of python to install older/compatible versions of blessed

[avylove]

Yeah, no actual code changes, so it should work. Do you think we should exclude 3.0 - 3.4 in python_requires?

[jquast]

Oh it’s fine as it is, just wanted to mention it :)