Merge pull request xtaci#38 from orthographic-pedant/spell_check/arbitrary

Fixed typographical error, changed arbitary to arbitrary in README.

Author: xtaci

README.md

@@ -27,7 +27,7 @@
     Prime test(trial division)
     Prime test(Miller-Rabin's method)
     2D Array
-    Arbitary Integer
+    Arbitrary Integer
     Linear congruential generator
     Maximum subarray problem