copied and customized from https://github.com/purcell/emacs.d
M-? ag-project C-M- kill-back-to-indent
[ggtags] M-] ggtags-find-reference M-. ggtags-find-tag-dwin M-* pop-tag-mark
[expand-region] C-= er/expand-region
[smex] M-. smex-find-function C-h-f smex-describe-function
[editing] C-c-J join-line C-c-P md/duplicate-up