simpeg/simpeg: Regularization, utils.plot2Ddata updates

Updates to Simple regularization from pr #807 commits by: @fourndo Summary Proposed modification to the model gradient measure for Simple and Sparse regularization. Normalized length scales are multiplying cell_weights before averaging to cell faces. Reduces the dependency of the model on cell size changes Still allows for IRLS weights to be mesh independent Default alpha's remain at 1 (takes care of length scales internally) Before After Additional Notes This pr also removed 2 VRM examples and the 1D MT example as they were failing. Issues #812, #814 document the issues, and pr's #813 and #815 have been started to resolve those issues. Updates to Utils.plot2Ddata from pr #808 commits from: @thast summary add shading options in utils.plot2Ddata Illustrations: On the docs example: On a mag dataset: Minor updates: small fix in the calling of mkvc in the regularization mesh (from #810, commits from @thast) update dependencies in the setup.py to remove indirect ones (from #188, commits from @lheagy