Add nans, infs, nans_like, infs_like convenience functions
Add more related functions
Add short note in doc string about dtype for non-numbers
Fix typo in doc string
Replace nans, nans_like, infs, infs_like with filled functions
Fix doc string
Add tests for filled_like function
Use commin method to compare array values
Use more idiomatic way of None-check
Add filled_like to doc string of test class
Add tests for zeros, ones, empty and filled
Comment test cases
Add doc string to creation test class
Do not compare string or unicode values
Fix Python 3 test cases for filled* functions