Release of 1.5.7

- e701c5422c969699b60ee10fe18c9b2d2b2bc063: Merge pull request #1411 from mattrjacobs/fix-bad-import
- 306cc39aeca58e5f7299e51aadbde7605443f818: Removed bad import that snuck in
- 7b3d2ceb62f6635dd8b793f3e65507aae194d51d: Merge pull request #1408 from crimeminister/bugfix/fix-clojure-key-name
- 0c7c6ae67b4e46337cdb7fd9a8835b9118dc700f: Fix typo in collapser options keyword name (from shared-fn to shard-fn)
- b0f5152f22156570424ed3787906f443ad30031d: Merge pull request #1407 from mattrjacobs/reset-percentile-snapshot-when-advancing-all-buckets
- c4cd610528473a70c57c773c4b7046debd537ed1: Clear the percentile snapshot whenever all buckets get cleared
- e7d23a3f8baff18b267739f0cc44a52d305e4d64: Merge pull request #1406 from mattrjacobs/fix-retry-deadlock
- b54a22b1d6b3175803ed770c44655aef2b4e68d9: Added unit test that demonstrates calling .retry() on an Observable produced by Hystrix does not result in deadlock
- 1bf896b5756928f761ffee18e920ddc1c05acd2a: Merge pull request #1405 from mattrjacobs/fix-comment-in-thread-pool-properties
- 27d0ca963e59096791aaa0158d1b5d0d39139bd1: Fix comment in HystrixThreadPoolProperties
- a735c80839992d2e98d50ffa5419aeb96f7d5c72: Merge pull request #1397 from michaelcowan/feature/optionally-raise-hystrix-runtime-exception
- 8b5a07575432480dd0b40488202d6c7ba5c33714: Merge pull request #1399 from mattrjacobs/add-property-to-control-maximum-thread-pool-size
- f68bd2f85359b8f4db26dcac966147184eacd4fa: Output setting around maximum thread pool size and whether this config is enabled
- 643d68089b7ee3ccf6ddca883e4f80362cf16c9d: Added flag to force users to opt-in to allowing core and maximum thread pool sizes to diverge
- 478c211afec863c46682af66bee57ebd01aba0fb: Removing change to BasicDefaultIgnoreExceptionsTest
- 12d19bdbc30b5761e388fc86f6fee96f8566eb7f: Adding raiseHystrixExceptions to DefaultProperties
- 8d8a8b330164c0d817b5de1afd8aa1c80fe0b3ed: Adding option to raise HystrixRuntimeException instead of cause
- 4e08f1ac2a576990ccad532615889344e2e35652: Merge pull request #1396 from mattrjacobs/unsubscribe-before-subscribe
- 5b1e4d6a34cf8592d0a4953f2cda741bfeefff55: If command is unsubscribed before any work starts, just return Observable.never()
- 487ee3af98da443220dfe0e4f6f00c9b89429d98: Merge pull request #1393 from ricardoletgo/master
- 141e182bd90b14cc0c0423ad52620b44bf112378: Merge pull request #1389 from dmgcodevil/javanica-iss1344
- 9f62a5f0f83f54413171f84a7cf9ebe7427e8a5e: Performance improvement in EnvUtils. Read "weavingMode" system property only one time.
- 1042f275fca07685d426f47ef56b20e94b40a583: iss1344: send fallback exception to client instead of primary command
- c175837403336e25662e041fdbe2679e58c8f54f: Merge pull request #1385 from monkey-mas/bump-jmh-gradle-plugin-to-0.3.1
- 9bbd6641660f034acec8359d3060299d59e172c0: Bump JMH gradle plugin to the latest version(0.3.1)
- 3fef4d73cb2f3ec0ae380c463561b1cf2dbd4873: Merge pull request #1382 from monkey-mas/bump-jmh-to-1.15
- 6a55d06948d19e6a26eb9677778d19d33166ba59: Bump JMH to the latest version(1.15)
- 7c42aa3ace76739fccd39704042fd147af5fc633: Merge pull request #1380 from mattrjacobs/add-jmh-test-when-circuit-opened
- da29bfdbb41795a383cc2740cbde8a9885abe4e2: Forgot to uncomment the non-Hystrix cases
- 881646ce6cc46725f2bc0446f33afe3bc57d0cd0: Add jmh tests for open-circuit case
- ad5e3f4e19a9df34a4ee369f8c0637144467017b: Merge pull request #1376 from bltb/cleanup-comments
- 4bc7b67668dfcb841d356a4406530c7797754a01: Remove outdated comments regarding thread keep alive.
- 66f13473559bd0b8610cf4509dc8e885cc1fa236: Merge pull request #1375 from mattrjacobs/remove-cancelled-tasks
- 324a9ab8403371ea2ffe88a6db771376c8ddea93: Remove cancelled work from the threadpool queue
- ae725f55829136157944bb8ed2996607cf1a030d: Merge pull request #1371 from mattrjacobs/allow-excess-threads-to-be-terminated
- c6fb4e1f896bda976a66bdfb7bc25bde1ff633a2: Add maximumSize to unit test
- b42e36c028f44489b5d7f2b32cf672ab075065e0: Add maximum size in configuration stream output
- 9d9f1ed0c214d7cc45465c823fbbae57d04f9ccf: Add maximumSize to Hystrix Configuration stream
- c21d586661aa0b246f933eea695737d12a87b4c2: Allow maximum size to affect HystrixThreadPool
- ef6b201b3552e2adc2c4547f35f95d4eefb26ff6: Add configuration for Hystrix thread pool maximumSize
- 069249c9afcc44c4e78d29f1fdd646214e17859a: Add v1.5.6 to CHANGELOG
