Add instructions

.github/CONTRIBUTING.md

@@ -16,11 +16,21 @@
 
 ### Development Setup
 
-```bash
+```
 git clone https://github.com/ArchiveBox/ArchiveBox
 cd ArchiveBox
-# Ideally do this in a virtualenv
-pip install -e '.[dev]'  # or use: pipenv install --dev
+python -m venv .venv
+. .venv/bin/activate
+pip install --upgrade bottle build flake8 pip pytest setuptools wheel
+pip install -r requirements.txt
+pip install -e .[sonic,ldap]
+```
+
+### Testing & linting
+
+```
+pytest -s --basetemp=tests/out --ignore=archivebox/vendor
+flake8 archivebox/ --config archivebox/.flake8 --count --show-source --statistics
 ```
 
 ### Getting Help