Add traces exporter to Jaeger (#1023)

* Add git-ignores.
* Add traces exporter to Jaeger (+tests).
* Add string tag with events' description to Jaeger exporter (+tests).
* Add integration test for Jaeger exporter (manually run).
diff --git a/settings.gradle b/settings.gradle
index e8a18cd..0d2617e 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -9,6 +9,7 @@
 include ":opencensus-exporter-trace-logging"
 include ":opencensus-exporter-trace-stackdriver"
 include ":opencensus-exporter-trace-zipkin"
+include ":opencensus-exporter-trace-jaeger"
 include ":opencensus-exporter-stats-signalfx"
 include ":opencensus-exporter-stats-stackdriver"
 include ":opencensus-exporter-stats-prometheus"
@@ -33,6 +34,7 @@
 project(':opencensus-exporter-trace-stackdriver').projectDir =
         "$rootDir/exporters/trace/stackdriver" as File
 project(':opencensus-exporter-trace-zipkin').projectDir = "$rootDir/exporters/trace/zipkin" as File
+project(':opencensus-exporter-trace-jaeger').projectDir = "$rootDir/exporters/trace/jaeger" as File
 project(':opencensus-exporter-stats-signalfx').projectDir = "$rootDir/exporters/stats/signalfx" as File
 project(':opencensus-exporter-stats-stackdriver').projectDir = "$rootDir/exporters/stats/stackdriver" as File
 project(':opencensus-exporter-stats-prometheus').projectDir = "$rootDir/exporters/stats/prometheus" as File