Merge pull request #23 from jpritikin/master

Better error msg
bugfix in SEM
reorder TOL for consistency
fixed MD nominal wrong starting slopes
update meta files and check fixes
fixed SEM Mstep tol
reduce EM tol, and test fixes
with the lower TOL an mstep of 1/1000 seems to work more effectively
drop.zeros option
update examples
Document meaning of misleading variable names