Added eigg function which is a wrapper to ggev

[selvavm]

This is to resolve #267. It is equivalent of eig(A,B) in Matlab

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@a561e5a). Click here to learn what that means.
The diff coverage is 85.71%.

@@            Coverage Diff            @@
##             master     #280   +/-   ##
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  Coverage          ?   88.86%           
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  Files             ?       71           
  Lines             ?     3727           
  Branches          ?        0           
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  Hits              ?     3312           
  Misses            ?      415           
  Partials          ?        0           

Impacted Files	Coverage Δ
lax/src/eig.rs	84.72% <81.66%> (ø)
ndarray-linalg/src/eig.rs	81.81% <100.00%> (ø)
ndarray-linalg/tests/eig.rs	100.00% <100.00%> (ø)

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[selvavm]

@termoshtt - could you please review this?

[selvavm]

@termoshtt - I noticed that eigh is using (a,b).eigh() and my implementation is a.eigg(&b). For the former there is no documentation, so it is hard to find.

I can change my implementation to be consistent with it. That is change mine to (a,b).eig(). How do you prefer?