Tutorial: added injectivity proof and Lemma pattern, breaking lines
Tutorial: added injectivity proof and Lemma pattern, breaking lines

hoheinzollern/FStar,FStarLang/FStar,A-Manning/FStar,hoheinzollern/FStar,A-Manning/FStar,FStarLang/FStar,hoheinzollern/FStar,FStarLang/FStar,A-Manning/FStar,hoheinzollern/FStar