从ruby 1.8 转移到 1.9之后的rspec用法变化 （rspec usage changes from ruby1.8 to ruby1.9)

in ruby 1.8, we use: $ rspec spec

however, in 1.9 , we have to specify the current path, e.g. $ rspec spec -I .    

more refer to :  http://stackoverflow.com/questions/11376718/require-lib-in-rspec-with-ruby-1-9-2-brings-no-such-file-to-load