Julia Benchmark

Add JuliaLang benchmark. 

Env. : Julia-v0.3.2, Ubuntu 14.04, i7-2600K CPU.
    Running 'ast.jl' : 0.63 ~ 0.68 seconds
    Running 'ast_tweak.jl' : 0.46 ~ 0.48 seconds
(PS. Use command 'julia', not 'julia-debug'.)