Tweak various things to make bundler happy.

Gemfile

@@ -3,7 +3,7 @@ source "https://rubygems.org"
 if !!File::ALT_SEPARATOR
   gemspec :name => 'rest-client.windows'
 else
-  gemspec
+  gemspec :name => 'rest-client'
 end
 
 group :test do

Rakefile

@@ -1,8 +1,6 @@
-begin
-  # optionally load `rake build/install/release tasks'
-  require 'bundler/gem_tasks'
-rescue LoadError
-end
+# load `rake build/install/release tasks'
+require 'bundler/setup'
+Bundler::GemHelper.install_tasks(:name => 'rest-client')
 
 require "rspec/core/rake_task"
 
@@ -58,7 +56,7 @@ def built_gem_path
 end
 
 namespace :windows do
-  spec_path = File.join(File.dirname(__FILE__), 'rest-client.gemspec')
+  spec_path = File.join(File.dirname(__FILE__), 'rest-client.windows.gemspec')
 
   WindowsPlatforms.each do |platform|
     namespace platform do
@@ -68,7 +66,7 @@ namespace :windows do
         begin
           ENV['BUILD_PLATFORM'] = platform
 
-          sh("gem build -V #{spec_path + '.windows'}") do |ok, res|
+          sh("gem build -V #{spec_path}") do |ok, res|
             if !ok
               puts "not OK: #{ok.inspect} #{res.inspect}"
             end

rest-client.windows.gemspec

@@ -5,7 +5,6 @@
 # Set $BUILD_PLATFORM when calling gem build with this gemspec to build for
 # Windows platforms like x86-mingw32.
 #
-
 s = eval(File.read(File.join(File.dirname(__FILE__), 'rest-client.gemspec')))
 
 platform = ENV['BUILD_PLATFORM'] || RUBY_PLATFORM
@@ -15,8 +14,6 @@ when /(mingw32|mswin32)/
   # ffi is needed for RestClient::Windows::RootCerts
   s.add_dependency('ffi', '~> 1.9.3')
   s.platform = platform
-else
-  raise NotImplementedError.new("Must specify $BUILD_PLATFORM")
 end
 
 s