Migrate to Kotlin 1.3 coroutines, drop experimental from package

* Features based on version 0.30.0
* Uses Kotlin version 1.3.0-rc-57
* Uses Kotlin/Native version 0.9.2
* Uses AtomicFu 0.11.9-eap13
* Replace SuccessOrFailure with Result
* Replace buildSequence and buildIterator with sequence and iterator
* Apply @BuilderInference on all builders (including extension methods to workaround inference bug)
diff --git a/core/kotlinx-coroutines-core/test/guide/example-context-02.kt b/core/kotlinx-coroutines-core/test/guide/example-context-02.kt
index 4d3eb0d..038102d 100644
--- a/core/kotlinx-coroutines-core/test/guide/example-context-02.kt
+++ b/core/kotlinx-coroutines-core/test/guide/example-context-02.kt
@@ -3,10 +3,10 @@
  */
 
 // This file was automatically generated from coroutines-guide.md by Knit tool. Do not edit.
-package kotlinx.coroutines.experimental.guide.context02
+package kotlinx.coroutines.guide.context02
 
-import kotlinx.coroutines.experimental.*
-import kotlin.coroutines.experimental.*
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
 
 fun main(args: Array<String>) = runBlocking<Unit> {
     launch(Dispatchers.Unconfined) { // not confined -- will work with main thread