numerically-indexed objects are not converted to Arrays

Per the [HOCON docs](https://github.com/typesafehub/config/blob/master/HOCON.md), Arrays should be lazily created from objects that have numerically indexed keys if the object cannot be mapped.

The following unit test should pass, but does not:
```
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Assert;
import org.junit.Test;

import java.io.IOException;
import java.util.List;

public class TestArrays {

    private String hoconOne = "list = [\"a\", \"b\"]";
    private String hoconTwo = "list.0 = \"a\"\nlist.2 = \"b\"";
    private String hoconThree = "list = {\"0\" : \"a\", \"2\" : \"b\"}";

    @Test
    public void testArrays() throws IOException {
        ObjectMapper mapper = new ObjectMapper(new HoconFactory());

        System.out.println("Mapping hocon of to Container class for:");
        System.out.println(hoconOne);
        Container cOne = mapper.readValue(hoconOne, Container.class);
        System.out.println("The Container class's list value is " + cOne.list);

        System.out.println("Mapping hocon of to Container class for:");
        System.out.println(hoconTwo);
        Container cTwo = mapper.readValue(hoconTwo, Container.class);
        System.out.println("The Container class's list value is " + cTwo.list);

        System.out.println("Mapping hocon of to Container class for:");
        System.out.println(hoconThree);
        Container cThree = mapper.readValue(hoconThree, Container.class);
        System.out.println("The Container class's list value is " + cThree.list);

        Assert.assertNotNull(cOne.list);
        Assert.assertNotNull(cTwo.list);
        Assert.assertNotNull(cThree.list);

        Assert.assertEquals(cOne.list, cTwo.list);
        Assert.assertEquals(cOne.list, cThree.list);
        Assert.assertEquals(cThree.list, cTwo.list);
    }

    public static class Container {
        public List<String> list;
    }
}
```
output:
```
Mapping hocon of to Container class for:
list = ["a", "b"]
The Container class's list value is [a, b]
Mapping hocon of to Container class for:
list.0 = "a"
list.2 = "b"

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
 at [Source: N/A; line: -1, column: -1] (through reference chain: com.jasonclawson.jackson.dataformat.hocon.Container["list"])
	at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:164)
	at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:691)
	at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:685)
	at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.handleNonArray(StringCollectionDeserializer.java:216)
	at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:164)
	at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:154)
	at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:19)
	at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:525)
	at com.fasterxml.jackson.databind.deser.impl.FieldProperty.deserializeAndSet(FieldProperty.java:106)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:242)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:118)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2986)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2091)
	at com.jasonclawson.jackson.dataformat.hocon.TestArrays.testArrays(TestArrays.java:26)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:211)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:67)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)


Process finished with exit code 255
```