Merge branch 'refactor'
Merge pull request #2 from AlekSi/master

Optimisations to decoder by AlekSi.
Merge pull request #3 from AlekSi/concurrent

Concurrent decoder
Refactor test.
Update git ignore patterns.
Add example, update README.
Allow concurrent invocations of Decode().

Use channels instead of slice+index for sync.
Unify tests/examples style.
Add benchmark for concurrent decode.