We can now use the gRPC gem directly from git.

With the release of bundler 1.10, we can now simplify the build steps, and use the git repository directly as a ruby gem, without having to install gRPC at all.
diff --git a/ruby/Gemfile b/ruby/Gemfile
index e75f0f6..65d3f0a 100644
--- a/ruby/Gemfile
+++ b/ruby/Gemfile
@@ -3,4 +3,4 @@
 
 source 'https://rubygems.org/'
 
-gemspec
+gem 'grpc', :git => 'https://github.com/grpc/grpc.git', :submodules => true, glob: 'src/ruby/*.gemspec'
diff --git a/ruby/README.md b/ruby/README.md
index 11b3d82..1fa958d 100644
--- a/ruby/README.md
+++ b/ruby/README.md
@@ -32,11 +32,6 @@
 -------
 
 - Clone this repository
-- Install gRPC Ruby using the brew-based installer
-```sh
-$ curl -fsSL https://raw.githubusercontent.com/tbetbetbe/homebrew-grpc/master/scripts/install | bash -s ruby
-```
-
 - Use bundler to install the example package's dependencies
 ```sh
 $ # from this directory