renames min and max to lo and hi

avoid shadowing
adds clipping function to IV
more global options
adds random_search_io method to Searcher
adds extrapolation code to DE
remove extraneous conversion to tuple
renames min and max to lo and hi everywhere
attaches random_search_io to the right class -_-
debugs clip -_-
renames frontier to _frontier in DE
cleans up crossover a bit
fixes clipping/assignment in extrapolation
fixes and simplifies _sample_frontier_exclude
cleans up and adds some imports
implements and calls in loop _update_frontier

first working version \o/
avoids divide by 0 errors in dtlz7

0s introduced by clipping in differential evolution
rdivs bests instead of eras
adds as_list parameter to rdiv.xtiles
implements rdiv with texttable instead of SB
fixes DE wrapping