release stable version

release stable version

Merge pull request #91 from xJakub/custom_start_times

Support custom startTime in spans

Merge pull request #81 from cawolf/extract-null-span-context

Extract null span context

Merge pull request #70 from dmnbars/master

remove unused properties

Merge branch 'phpunit'

Opentracing beta5 version

Merge pull request #37 from jukylin/fix_sp_error

fix issues 35

Merge pull request #36 from Liv1020/fix-istio-1.1.3

fix istio 1.1.3 jaeger traceID 32-bit overflow

Merge pull request #31 from jukylin/reuse_udpclient

reuse udp client