Added some forgotten keys to README
Fixed some mistakes in README
Improve Helm configuration

The current prelude-helm only uses a single command of Helm, which
is a waste given how Helm contains many other commands. When
prelude-helm is activated, users should be able to utilize all of these
useful commands. If a user wants to use Helm, he will want to use all of
its features anyway.

prelude-helm is configured that it is able to be used with this [guide](http://tuhdo.github.io/helm-intro.html).
Merge pull request #653 from tuhdo/master

Improve Helm configuration
Flat index with python imenu
Allow enable/disable global helm key bindings

Since some users prefer using default Prelude commands, a new global
mode is defined: prelude-global-helm-mode. When activate, Helm binds
some global key bindings to its own commands. When deactivate, Helm
removes the bindings and Prelude uses the default bindings.
Merge pull request #657 from tuhdo/master

Allow enable/disable global helm key bindings
Merge pull request #651 from k1-hedayati/added-some-forgotten-keys-to-readme

Added some forgotten keys to README
Merge pull request #655 from toctan/python-imenu

Flat index with python imenu
Merge remote-tracking branch 'upstream/master'