Add concurrency topic (#480)

ErikSchierboom · robkeim · commit 0146e536fc1e · 2016-12-24T20:36:53.000+01:00
diff --git a/TOPICS.txt b/TOPICS.txt
@@ -46,6 +46,7 @@ Problem areas
 -------------
 Algorithms
 Bitwise operations
+Concurrency
 Domain-specific languages
 Files
 Filtering
