Add test suite converted to rspec

Update gemfiles for travis builds. Minor spec fixes for 1.8.7 - not passing on 1.8.7 yet

Add common gemfile

Author: cheald

Gemfile

@@ -1,16 +1,4 @@
-source 'https://rubygems.org'
+eval File.read(File.expand_path('../gemfiles/Gemfile.common', __FILE__)), nil, 'Gemfile.common'
 gemspec
 
-gem 'rake'
-gem 'mongo',    '~> 1.8'
-gem 'bson_ext', '~> 1.8'
-gem 'multi_json', '~> 1.2.0'
-
-group :test do
-  gem 'rails',             '~> 3.2.0'
-  gem 'jnunemaker-matchy', '~> 0.4', :require => 'matchy'
-  gem 'shoulda',           '~> 2.11'
-  gem 'timecop',           '~> 0.3'
-  gem 'mocha',             '~> 0.10.0'
-  gem 'rack-test',         '~> 0.6'
-end
+gem 'rails', '~> 3.2.0', :group => :test

Rakefile

@@ -1,16 +1,19 @@
 require 'rubygems'
 require 'bundler/setup'
 require 'rake'
-require 'rake/testtask'
 require File.expand_path('../lib/mongo_mapper/version', __FILE__)
 
-Rake::TestTask.new(:test) do |test|
-  test.libs      << 'lib' << 'test'
-  test.pattern   = 'test/**/test_*.rb'
+begin
+  require 'rspec/core/rake_task'
+  RSpec::Core::RakeTask.new(:spec) do |spec|
+    spec.pattern = 'spec/**/*_spec.rb'
+    spec.rspec_opts = ['--color']
+  end
+  task :default => :spec  
+rescue LoadError
+  nil
 end
 
-task :default => :test
-
 desc 'Builds the gem'
 task :build do
   sh "gem build mongo_mapper.gemspec"