Corrected four minor typos in README.md

Line 34: so `a{/b/c,bcd}` would expand into `a/b/c` and `abc*d*\.
Line 39: Matches 0 or more characters in a sin*g*le path portion
Line 103: glob.hasMagic(patter*n*, [options])
Line 134: Create a Glob object by instanti*ati*ng the `glob.Glob` class.