change init values for success to True, errorbars to False

Merge pull request lmfit#162 from andyfaff/diffev

ENH: adding differential evolution as a fitting method

use py3.4 in upload script

updated README, using rst formatting

add example of using per-iteration callback

tweak doc html header

more doc on models

update version to 0.7.4

version 0.7.3

delete old file