add Havlak benchmark

+# Havlak benchmark: https://code.google.com/p/multi-language-bench/
 +# Crystal Implementation
 +
 +# Intel i5 2.5GHz
 +# c++: 28.8s 147Mb
 +# java: 33.7s 909Mb
 +# crystal: 35.1s 387Mb
 +# go: 67.7s 456Mb 
 +# scala: 66.8s 316Mb