Update for current python versions

Author: kotfu

CONTRIBUTING.md

@@ -16,46 +16,44 @@ suite against multiple python versions. I recommend
 these various versions. If you are a Windows user, `pyenv` won't work for you,
 but [conda](https://conda.io/) can also be used to solve this problem.
 
-This distribution includes a shell script `build-pyenvs.sh` which
-automates the creation of these environments.
+This distribution includes a shell script `build-pyenvs.sh` which automates
+the creation of these environments.
 
 If you prefer to create these virtual envs by hand, do the following:
 ```
 $ cd cmd2_abbrev
+$ pyenv install 3.8.0
+$ pyenv virtualenv -p python3.8 3.8.0 cmd2-3.8
 $ pyenv install 3.7.0
-$ pyenv virtualenv -p python3.7 3.7.0 cmd2-3.7
+$ pyenv virtualenv -p python3.7 3.7.5 cmd2-3.7
 $ pyenv install 3.6.5
-$ pyenv virtualenv -p python3.6 3.6.5 cmd2-3.6
+$ pyenv virtualenv -p python3.6 3.6.9 cmd2-3.6
 $ pyenv install 3.5.5
-$ pyenv virtualenv -p python3.5 3.5.5 cmd2-3.5
-$ pyenv install 3.4.8
-$ pyenv virtualenv -p python3.4 3.4.8 cmd2-3.4
+$ pyenv virtualenv -p python3.5 3.5.8 cmd2-3.5
 ```
 
 Now set pyenv to make all three of those available at the same time:
 ```
-$ pyenv local cmd2-3.7 cmd2-3.6 cmd2-3.5 cmd2-3.4
+$ pyenv local cmd2-3.8 cmd2-3.7 cmd2-3.6 cmd2-3.5
 ```
 
 Whether you ran the script, or did it by hand, you now have isolated
-virtualenvs for each of the major python
-versions. This table shows various python commands, the version of
-python which will be executed, and the virtualenv it will utilize.
+virtualenvs for each of the major python versions. This table shows various
+python commands, the version of python which will be executed, and the
+virtualenv it will utilize.
 
 | Command     | python | virtualenv |
 | ----------- | ------ | ---------- |
-| `python`    | 3.7.0  | cmd2-3.6   |
-| `python3`   | 3.7.0  | cmd2-3.6   |
-| `python3.7` | 3.7.0  | cmd2-3.7   |
-| `python3.6` | 3.6.5  | cmd2-3.6   |
-| `python3.5` | 3.5.5  | cmd2-3.5   |
-| `python3.4` | 3.4.8  | cmd2-3.4   |
-| `pip`       | 3.7.0  | cmd2-3.6   |
-| `pip3`      | 3.7.0  | cmd2-3.6   |
-| `pip3.7`    | 3.7.0  | cmd2-3.7   |
-| `pip3.6`    | 3.6.5  | cmd2-3.6   |
-| `pip3.5`    | 3.5.5  | cmd2-3.5   |
-| `pip3.4`    | 3.4.8  | cmd2-3.4   |
+| `python`    | 3.8.0  | cmd2-3.8   |
+| `python3`   | 3.8.0  | cmd2-3.8   |
+| `python3.7` | 3.7.5  | cmd2-3.7   |
+| `python3.6` | 3.6.9  | cmd2-3.6   |
+| `python3.5` | 3.5.8  | cmd2-3.5   |
+| `pip`       | 3.8.0  | cmd2-3.8   |
+| `pip3`      | 3.8.0  | cmd2-3.8   |
+| `pip3.7`    | 3.7.5  | cmd2-3.7   |
+| `pip3.6`    | 3.6.9  | cmd2-3.6   |
+| `pip3.5`    | 3.5.8  | cmd2-3.5   |
 
 
 ## Install Dependencies
@@ -68,23 +66,24 @@ $ pip install -e .[dev]
 This command also installs `cmd2-abbrev` "in-place", so the package points to
 the source code instead of copying files to the python `site-packages` folder.
 
-All the dependencies now have been installed in the `cmd2-3.7`
+All the dependencies now have been installed in the `cmd2-3.8`
 virtualenv. If you want to work in other virtualenvs, you'll need to manually
 select it, and install again::
 
-   $ pyenv shell cmd2-3.4
+   $ pyenv shell cmd2-3.6
    $ pip install -e .[dev]
 
 ## Common Development Tasks
 
 This project uses many other python modules for various development tasks,
 including testing, linting, building wheels, and distributing releases. These
 modules can be configured many different ways, which can make it difficult to
-learn the specific incantations required for each project you are familiar with.
+learn the specific incantations required for each project you are familiar
+with.
 
-This project uses [invoke](<http://www.pyinvoke.org>) to provide a clean,
-high level interface for these development tasks. To see the full list of
-functions available:
+This project uses [invoke](<http://www.pyinvoke.org>) to provide a clean, high
+level interface for these development tasks. To see the full list of functions
+available:
 ```
 $ invoke -l
 ```
@@ -94,9 +93,9 @@ You can run multiple tasks in a single invocation, for example:
 $ invoke clean docs sdist wheel
 ```
 
-That one command will remove all superflous cache, testing, and build
-files, render the documentation, and build a source distribution and a
-wheel distribution.
+That one command will remove all superflous cache, testing, and build files,
+render the documentation, and build a source distribution and a wheel
+distribution.
 
 For more information, read `tasks.py`.