Fixes Issue#443

[Supriya1702]

Description

This PR does the following:

• If truncation=None for broadening_method='voigt' for optimization='simple' or 'min-RMS method it raises NotImplementedError
• If truncation is negative it raises value error
• Allows computation for broadening_method == "voigt" and truncation == None for optimization=None

Fixes #443

[anandxkumar]

Tested for different cases, works fine on my end, Good job!
@erwanp should truncation=None work for optimization=None for broadening_method='voigt'?

[erwanp]

Hello, good work!

1. are you sure optimization=None is implemented?

2. We'd need a quick test, for instance one making sure an error is raised if negative truncation is given, and one making sure truncation=None does what we want. If you need help implementing tests please reach out on Slack

[Supriya1702]

Hello @erwanp, I added test for checking negative truncation and truncation==None. I found that truncation=None works for broadening_method='voigt' for optimization=None but gives error when used fft. Oppositely in optimization='simple, truncation=None works for fft but fails for voigt, so I added the tests accordingly

[erwanp]

Great, merging !