TST: split up tests/plotting/test_frame.py into subdir & modules

[jreback]

we should split up this test file into a separate subdir and multiple test modules for better groking. first PR should be a straight move, then can split (or all in one is ok)

[nthiagar]

Hello @jreback,
I am a new contributor and I would like to tackle this as my first issue. I have familiarized myself with Python and Github. Would you be willing to guide me through the process?
Thank you

[iahsanujunda]

I would also like to help if needed

[iahsanujunda]

take

[iahsanujunda]

@jreback I have created PR for putting tests/plotting/test_frame.py into tests/plotting/frame/test_frame.py first. How should we proceed on splitting this into sub-modules?

[rajalakshmi139]

Hi,
I am new to open source and would like to help. I have decent experience with Python and Github.

[Mikhaylov-yv]

take