Update readme

Author: 4OH4

README.md

@@ -13,19 +13,19 @@ Python 3 and the following packages (all available via `pip`):
 
 Or install via the `requirements.txt` file:
 
-```pip install -r requirements.txt```
+    pip install -r requirements.txt
 
 ## Running test cases
 Tests should be run from the command line, in the repository root.
 
 ### Doctest
 Doctests are executed for a single module at a time. The command runs the tests in database.py (for example):
 
-```python -m doctest -v src/database.py```
+    python -m doctest -v src/database.py
 
 The `-v` argument requests verbose output - otherwise it only reports test failures.
 
 ### Pytest
 To run all test cases (in the `tests/` folder):
 
-```python -m pytest tests```
+    python -m pytest tests