Updated version to 0.2.1

Updated crates version to 0.2.0

Merge pull request wasmerio#52 from wasmerio/fix/emscripten-env

Fix support for env vars (put, set, unset)

Merge pull request wasmerio#53 from wasmerio/feature/run-lua-wasm

Running Lua

Improved index page

Fixed accept socket call

Merge pull request wasmerio#24 from wasmerio/feature/type-safety

Add VarArgs newtype to simplify emscripten varargs.