put setattr() in try/except

Merge pull request lmfit#257 from lmfit/exprmodel_noprefix

add warning and doc for prefix in ExpressionModel

Merge pull request lmfit#255 from danielballan/fix-ipyfitter

Fix ipyfitter

Merge pull request lmfit#253 from lmfit/rc_090

update docs, near ready for for 0.9.0rc

Merge pull request lmfit#195 from newville/master

add dump()/load() to Parameters class

Merge pull request lmfit#188 from newville/master

doc: add start of FAQ, and better links to support

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