REF:  Move _handle solo from closure to top level function.
CLN: A bit clearer on next Y for g_p.
PAPER: Cleanup and more content.
ENH: Add range method to ecdf
REF:  Estimate wage distribution via simulation.

This is a major refactoring of eqs 17 & 18 in DH.

I've removed the SRS for the distribution and am instead
modeling it via simulation.  This knocks on to output.

The results seem more sensible so I'm going with it.

squash! REF:  Estimate wage distribution via simulation.
REF:  Move back to using u_ in the calcuation for utility.
BUG:  I wasn't updating the parameters...
CLN:  More cleanup following refactor.
ENH:  Attach metadata to ecdfs.
ENH: Helper to get wage dist
API: Make aggL a kwarg in Python land and a positional arg in Cython
API/REF: Add an outer wrapper to handle aggL iteration.
PARAM: Updated parameters.  Mainly for nicer grid.
BUG/TST:  Update test to reflect change back to u_ from up