4.1.0-rc2

• Added InstrumentedHttpClientConnectionManager constructor with HttpClientConnectionOperator #1294
• Add counter for active connections (#1291)
• Allow Java 8 Duration for Timer#update (#1298)
• jvm: Params to include sync info in thread dump (#1304)
• Make the relationship between the Reporter and Closeable interfaces explicit (#1307)
• MetricRegistry: make registerAll with prefix public (#1308)
• DefaultObjectNameFactory: use type, be a bit more conservative about quoting (#1310)