Fix fourtech epslevel

Fixes #960. 

Additionally, changes were made to the way epslevel is updated in the `fourtech' methods `diff`, `times`, `qr`, and  `cumsum` to match what is done in `chebtech` for these methods.  

The 2/3 power check for the tail in `classicCheck` has also been changed to 1 to also match what is done in `chebtech/classicCheck`.

Tolerances in test were also updated so that everything passes.