New contrib module: rxjava-async-util

Home for async utility functions with juc.Future, Actions, Functions etc that don’t need to be in rxjava-core.

As per discussions at:

- ReactiveX/RxJava#646 (comment)
- ReactiveX/RxJava#645 (comment)
- ReactiveX/RxJava#622 (comment)

build.gradle

@@ -0,0 +1,20 @@
+apply plugin: 'osgi'
+
+sourceCompatibility = JavaVersion.VERSION_1_6
+targetCompatibility = JavaVersion.VERSION_1_6
+
+dependencies {
+    compile project(':rxjava-core')
+    testCompile project(":rxjava-core").sourceSets.test.output 
+    provided 'junit:junit-dep:4.10'
+    provided 'org.mockito:mockito-core:1.8.5'
+}
+
+jar {
+    manifest {
+        name = 'rxjava-async-util'
+        instruction 'Bundle-Vendor', 'Netflix'
+        instruction 'Bundle-DocURL', 'https://github.com/Netflix/RxJava'
+        instruction 'Import-Package', '!org.junit,!junit.framework,!org.mockito.*,*'
+    }
+}