Improvement: Update dev instructions (#172)

Update dev instructions

Author: psyclaudeZ

CONTRIBUTING.md

@@ -9,21 +9,20 @@ The team welcomes contributions!  To make code changes to one of the Conjure rep
 ## Local Development
 
 ### Prerequisites
-- Python2 (On macOS: `brew install python2`)
 - Python3 (On macOS: `brew install python3`)
 - [pipenv](https://github.com/pypa/pipenv) (`pip3 install pipenv`)
 
-_We recommend the free [VSCode](https://code.visualstudio.com/) editor to work on python projects._
+_We recommend [VSCode](https://code.visualstudio.com/) to work on python projects._
 
 ### One-time setup for development
 
 1. Fork the repo
-1. Create the virtual environment `PIPENV_VENV_IN_PROJECT=1 pipenv --python 3 shell`
-1. Install all dependencies `pipenv install --dev`
-1. Download and generate integration test dependencies `./scripts/prepare_integration_tests.sh`
-1. From within a pipenv shell, run `code .` to open a new VSCode window.
+2. Create the virtual environment `PIPENV_VENV_IN_PROJECT=1 pipenv --python 3 shell`
+3. Install all dependencies `pipenv install --dev`
+4. Download and generate integration test dependencies `./scripts/prepare_integration_tests.sh`
+5. From within a pipenv shell, run `code .` to open a new VSCode window.
 
 ### Development tips
 
 - Use `python setup.py format` to quickly reformat all code using [Black](https://github.com/ambv/black)
-- Use `tox` to run all tests using both python 2 and 3
+- Run `tox` to run all unit tests, integration tests, mypy, and lint. Use `-e` for individual tasks e.g. `tox -e py3`, `tox -e lint`.