multibyte language support of selector name

This Pull Request is multibyte language support of describe and it and context string.

e.g.
describe("テスト"){ it("確認"){...} }
// SelectorName is "テスト__確認" (Japanese).

describe("Một thử nghiệm"){ it("xác nhận"){...} } 
// SelectorName is Một_thử_nghiệm__xác_nhận (Vietnamese).

describe("测试"){ it("确认"){...} }
// SelectorName is 测试__确认 (Chinese).

 describe("테스트"){ it("확인") {...} }
// SelectorName is 테스트__확인 (Korean)

You can write Test using multibyte language based on Unicode. :)
(Cannot use Unicode Pictogram. Pictogram are converted to "_")