Unsafe YAML loading

In `routines`, the YAML loading functionality relies on the out dated API, which apparently is unsafe/unsecure:

```python
tests/test_database.py::test_db_io
  /home/kelvin/Python/PySpecTools/pyspectools/routines.py:92: PendingDeprecationWarning:
  
  
  load will be removed, use
  
    yaml=YAML(typ='unsafe', pure=True)
    yaml.load(...)
  
  instead
```