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