Added extra diagnostics

- Check if say or espeak are installed
- Check if all pip requirements were installed
Will this work, even if I didn't install the python package via pip but via the package manager? (I guess this works, but I'm not completely sure). An alternative could be to use `importlib.import_module()` and catch ImportErrors.

Also, we should avoid direct calls via `subprocess.call()` as much as possible (for cross-platform compatibility). So if you think that `pip` is the way to go, then please do something like:
```Python
from pip.commands.show import search_packages_info
packages = ['requests','argparse']
print(list(search_packages_info(packages)))
```