Switch from failure::Fail to std's Error trait

[jturner314]

#118 simplified the LinalgError enum but also changed it from implementing Error to implementing Fail. This PR keeps the simplifications but changes it to implement Error again. (I also renamed the LapackFailure variant to Lapack, renamed the ShapeFailure variant to Shape and changed it to a tuple, and removed the braces from MemoryNotCont.) IMO this is better for a few reasons:

1. failure is "experimental" and "currently evolving", so while it may be fine for an end-user application, I don't think we should use it for a library like ndarray-linalg.
2. The standard library's Error is being updated based on the failure experiment to resolve most of the issues with the old version of Error. (RFC 2504) In stable, the .source() method has already been added, .cause() is planned to be deprecated in 1.33, and .description() is "soft-deprecated".
3. It's annoying to have to call .compat() to get something that implements Error.

[termoshtt]

failure is "experimental" and "currently evolving", so while it may be fine for an end-user application, I don't think we should use it for a library like ndarray-linalg.

This makse sense. Thanks PR.