docs: update dev docs (#87)

## Which problem is this PR solving?

- resolves some dev doc gaps identified on #77

## Short description of the changes

- replaces the poetry commands in DEVELOPING with the simpler make
  variants we've added to the project
- state minimum Python version in README
- link to DEVELOPING from README

## How to verify that this has the expected result

- Run all the make commands
- Run 'em with remake, too

DEVELOPING.md

@@ -3,30 +3,31 @@
 Requires [poetry](https://python-poetry.org/docs/) for dependency management and packaging.
 Run `poetry --version` to verify it is installed. A minimum of Poetry 1.2 is required.
 
-## Package setup and build
+Our development workflow leverages a `Makefile` to define "targets" for most of the routine development tasks for this project, like running tests or producing a build.
+These targets can be run with the venerable build tool [GNU Make](https://www.gnu.org/software/make/) or one of its variants, like [remake](https://remake.readthedocs.io/en/latest/).
 
-```bash
-poetry install
-poetry build
-```
+While the `make` command is possibly already installed on your computer, we recommend `remake` which extends GNU Make to add profiling, debugging, improved error messages, and usage help text for targets.
+`remake --tasks` will output a list of the commonly-used make targets.
+`remake` may be substituted for `make` in any of the commands below.
 
-## Testing
+## Package setup and build
 
 ```bash
-poetry run pytest tests
+make install
+make build
 ```
 
-or
+## Testing
 
 ```bash
-poetry run coverage run -m pytest tests
+make test
 ```
 
 ## Linting & Code Style
 
 ```bash
-poetry run pylint src
-poetry run pycodestyle src tests
+make lint
+make style
 ```
 
 ## Troubleshooting

README.md

@@ -7,12 +7,17 @@
 This is Honeycomb's Distribution of OpenTelemetry for python.
 It makes getting started with OpenTelemetry and Honeycomb easier!
 
+## Requirements
+
+* Python 3.7 or higher
+
 ## Getting Started
 
 Honeycomb's Distribution of OpenTelemetry for python allows you to streamline configuration and to instrument as quickly and easily as possible.
 
 - [Documentation](https://docs.honeycomb.io/getting-data-in/opentelemetry/python/)
 - [Examples](/examples/)
+- See [DEVELOPING.md](/DEVELOPING.md) for additional instructions for building and testing this project in development.
 
 ## Why would I want to use this?