YamlSequence: print without extra newLine

first of all, thank you for sure a great project ! I really love it!

So according to our specs, we should emit complex sequences without extra newLine like this:

```
- item : Super Hoop
quantity: 1
- item : Basketball
quantity: 4
- item : Big Shoes
quantity: 1
```

but i can't find out how to achive it:

```
YamlSequenceBuilder sequence = Yaml.createYamlSequenceBuilder();

YamlMappingBuilder compactNestedMapping = Yaml.createYamlMappingBuilder();
compactNestedMapping = compactNestedMapping.add("item", "Super Hoop");
compactNestedMapping = compactNestedMapping.add("quantity", "1");

sequence = sequence.add(compactNestedMapping.build());
```

always produce :

```
-
item: Super Hoop
quantity: 1
```

i am totally sure, i do something wrong

Thanks for any ideas