Add test for IDs order.
Extract OSMData (PrimitiveBlock) decoder.
Move zlib decompressing.
Preallocate space for zlib decoding.
Return decoded objects.
Do not share decode result.
Make `go vet` happy.
Decode OSMData concurrently.
Check Start error in tests.
Merge pull request #3 from AlekSi/concurrent

Concurrent decoder