Update README.md

Sorry, I read CONTRIBUTING.md now.
My pull request was closed.

I have this messages when I try to run `bundle install`

```bash
% bundle install
Fetching source index from https://rubygems.org/
Resolving dependencies...
Could not find gem 'kendo-rails (>= 0) ruby' in the gems available on this machine.
```

and I try to run `gem install kendo-rails`
```bash
% gem install kendo-rails
ERROR:  Could not find a valid gem 'kendo-rails' (>= 0) in any repository
ERROR:  Possible alternatives: kendoui-rails, kanso-rails, koko_rails, pen-rails, neo-rails
```

The gem `kendo-rails` didn't exsist.
Perhaps it is typo of `gem 'kendoui-rails'` ?