Polish README.md
Polish README.md

Polish some sentences and correct some typos.
Soyn/CLRS,semsevens/CLRS,Soyn/CLRS,semsevens/CLRS,Soyn/CLRS,Jingru/CLRS,gzc/CLRS,gzc/CLRS,Jingru/CLRS,Jingru/CLRS,gzc/CLRS,semsevens/CLRS