Benchmarking suite

[chfast]

1. It will be based on evmone-bench: https://github.com/ethereum/evmone/tree/master/test/bench
2. It will use Google Benchmark library.
3. It will load all wasm binary files from a directory (with subdirectories).
4. Each wasm file can have matching *.inputs file with inputs (see evmone: https://github.com/ethereum/evmone/blob/master/test/benchmarks/sha1_divs.inputs).
   1. Test cases are separated by empty lines.
   2. Each test cases has following lines:
      1. Test case name.
      2. Exported function name to be executed.
      3. Function arguments.
      4. Initial memory, hex encoded.
      5. Expected result.
      6. Expected memory after execution.

[chfast]

Done in #74.