Add pyc and pys fixtures

[ElSnoMan]

#248

Changes

• add pyc - a class-scoped Pylenium fixture

• add pyc_config - a class-scoped PyleniumConfig

• add pys - a session-scoped Pylenium fixture

• add pys_config a session-scoped PyleniumConfig

Testing

All were tested using the tests within test_flows.py, but I got some interesting results:

• session-scoped tests were about as fast as the default function-scoped tests (~12 seconds)
• class-scoped tests were very slow... (~60 seconds)

💡 To be clear, you can use session- or function-scoped tests in a Test Class