Content-Type: text/html
Content-Length: 342

Update current:
a -> 1
b -> 2
c -> 3
{
	"a":"-",
	"b":"2",
	"c":"3"
}
Insert:
a -> 1
b -> 2
c -> 3
d -> 4
{
	"a":"1",
	"b":"2",
	"c":"3",
	"d":"4"
}
Delete current:
a -> 1
b -> 2
c -> 3
{
	"b":"2",
	"c":"3"
}
Delete before current:
a -> 1
delete: b -> 2
c -> 3
{
	"b":"2",
	"c":"3"
}
Delete after current:
a -> 1
c -> 3
{
	"a":"1",
	"c":"3"
}