Kafka 0.10

[pulyaevskiy]

Pull request to track progress of refactoring to 0.10 protocol.
Everything below is a minimum required to get to the first public alpha.

Core:

• Refactor and cleanup binary protocol layer
• Add request timeout to Session
• Complete implementation of all APIs for 0.10 protocol version
  • MessageSet and Message (v1)
  • TopicMetadata
  • Produce (v2)
  • Fetch (v2)
  • ListOffset (v1)
  • GroupCoordinator
  • OffsetCommit (v2)
  • OffsetFetch (v1)
  • JoinGroup (v1)
  • SyncGroup
  • Heartbeat
  • LeaveGroup
  • ListGroups
  • DescribeGroups
  • ApiVersions
  • CreateTopics
  • DeleteTopics
• Introduce basic serialization interface
• Dynamic api version resolution
• Testing facilities

Producer:

• Minimum implementation
• Batch sends
• Expose minimum configuration options
• Handle maxRequestSize and split requests
• Control in-flight requests per connection
• GZip

Consumer:

• Minimum implementation
• Make Consumer a StreamIterator
• Heartbeats
• Expose configuration options
• Handle broker rebalance and migration of partitions within Kafka cluster
• GZip

General:

• Cleanup public interface and exports.
• Resolve all critical TODOs left in the code.
• Update Travis build
• Update documentation

Todo:

• Add more bullet points above

[codecov]

Codecov Report

Merging #13 into master will decrease coverage by 9.55%.
The diff coverage is 79.44%.

@@            Coverage Diff             @@
##           master      #13      +/-   ##
==========================================
- Coverage   88.59%   79.03%   -9.56%     
==========================================
  Files          22       27       +5     
  Lines         973     1269     +296     
==========================================
+ Hits          862     1003     +141     
- Misses        111      266     +155

Impacted Files	Coverage Δ
lib/src/util/crc32.dart	100% <ø> (ø)	⬆️
lib/src/versions.dart	100% <100%> (ø)
lib/src/session.dart	100% <100%> (+10.09%)	⬆️
lib/src/util/group_by.dart	100% <100%> (ø)
lib/src/errors.dart	24.54% <24.54%> (ø)
lib/src/util/tuple.dart	40% <40%> (ø)
lib/src/serialization.dart	50% <50%> (ø)
lib/src/consumer_group.dart	50% <53.33%> (-37.72%)	⬇️
lib/src/messages.dart	63.63% <63.63%> (ø)
lib/src/consumer.dart	67.46% <69.67%> (-10%)	⬇️
... and 39 more

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