Merge pull request bbatsov#649 from k1-hedayati/update-readme-for-sme…

…x-major-mode-binding

Added M-X to README

README.md

@@ -258,6 +258,7 @@ Keybinding         | Description
 <kbd>C-x m</kbd>   | Start `eshell`.
 <kbd>C-x M-m</kbd> | Start your default shell.
 <kbd>C-x C-m</kbd> | Alias for `M-x`.
+<kbd>M-X</kbd>     | Like `M-x` but limited to commands that are relevant to the active major mode.
 <kbd>C-h A</kbd>   | Run `apropos` (search in all Emacs symbols).
 <kbd>C-h C-m</kbd> | Display key bindings of current major mode and descriptions of every binding.
 <kbd>M-/</kbd>     | Run `hippie-expand` (a replacement for the default `dabbrev-expand`).