* fix qr and sign edge cases
qr() was throwing an error if the pivots of a matrix were zero.
This commit fixes that and ensures that the results are consistant
with wolfram alpha.
Whilst doing this I found a bug in complex.js, I have added a work
around but we should flag this upstream.
I also addressed the long standing concerns about assert statements
within the body of the qr function.
Fixes#1669Fixes#942
* further improvements to qr and sign
mainly fixing things I got wrong in previous commit
* add array test
* fix: remove only from tests and disallow
Uses mochas `--forbid-only` flag as advised by
https://github.com/standard/standard/issues/988