Remove generated .gem files after installing a gem from a :path

Closes rubygems#286

lib/bundler/source.rb

@@ -278,6 +278,8 @@ def generate_bin(spec)
         end
 
         Bundler.ui.warn "The validation message from Rubygems was:\n  #{e.message}"
+      ensure
+        Dir.chdir(gem_dir){ FileUtils.rm_rf(File.join(gem_dir, gem_file)) }
       end
 
     end

spec/install/path_spec.rb

@@ -84,7 +84,7 @@
     should_be_installed "foo 1.0"
   end
 
-  it "setups up executables" do
+  it "sets up executables" do
     pending_jruby_shebang_fix
 
     build_lib "foo" do |s|
@@ -100,6 +100,16 @@
     out.should == "1.0"
   end
 
+  it "removes the .gem file after installing" do
+    build_lib "foo"
+
+    install_gemfile <<-G
+      gem 'foo', :path => "#{lib_path('foo-1.0')}"
+    G
+
+    lib_path('foo-1.0').join('foo-1.0.gem').should_not exist
+  end
+
   describe "block syntax" do
     it "pulls all gems from a path block" do
       build_lib "omg"