Ensured that the C Driver will not be loaded unless the platform supports it--it will only be loaded on little endian

lib/bson.rb

@@ -45,6 +45,8 @@ else
   begin
     # Need this for running test with and without c ext in Ruby 1.9.
     raise LoadError if ENV['TEST_MODE'] && !ENV['C_EXT']
+    #raise LoadError unless little endian
+    raise LoadError unless [1,0,0,0].pack("i").bytes.first==1
     require 'bson_ext/cbson'
     raise LoadError unless defined?(CBson::VERSION)
     if CBson::VERSION < MINIMUM_BSON_EXT_VERSION