check k?

[derekbeaton]

Should I check k before it's entered for various silly values, and then stop/silently work if they are silly values?

[derekbeaton]

this now only needs to occur in the g*() and tolerance_*() functions

I think I will need to formally check them for eigen, but not necessarily for svd because that allows for k.

but I should be consistent and provide consistent messaging to the user. so I'll put some checks of k into the tolerance_* functions (or make a k-checker function which either stops or passes k back and use it where ever)