corrected some typos in readme
corrected some typos in readme

michaelhogg/jasmine-custom-message,avrelian/jasmine-custom-message,damianfarina/jasmine-custom-message,avrelian/jasmine2-custom-message,avrelian/jasmine-custom-message,michaelhogg/jasmine-custom-message,avrelian/jasmine2-custom-message,damianfarina/jasmine-custom-message