Adds style option for nested sequence

Each nested array will be in a new line if true
-
  - 1

else
- - 1

lib/js-yaml/dumper.js

@@ -118,6 +118,7 @@ function State(options) {
   this.noRefs        = options['noRefs'] || false;
   this.noCompatMode  = options['noCompatMode'] || false;
   this.condenseFlow  = options['condenseFlow'] || false;
+  this.nestedSeqBlocks = options['nestedSeqBlocks'] || false;
 
   this.implicitTypes = this.schema.compiledImplicit;
   this.explicitTypes = this.schema.compiledExplicit;
@@ -550,6 +551,10 @@ function writeBlockSequence(state, level, object, compact) {
         _result += '- ';
       }
 
+      if (state.nestedSeqBlocks && Array.isArray(object[index])) {
+        _result += generateNextLine(state, level + 1);
+      }
+
       _result += state.dump;
     }
   }