update rust from 1.11 to 1.15, fixed #119
update rust from 1.11 to 1.15, fixed #119

kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks,kostya/benchmarks