rename tag for nbt_type to list instead of noarray and add documentation

nbt/README.md

@@ -1,4 +1,53 @@
 # NBT
-This package implement the Named Binary Tag format of Minecraft.
+This package implement the Named Binary Tag format of Minecraft. It supports all formats
+of NBT including compact arrays for longs.
+
+# Usage
+For the following NBT tag:
+
+```
+TAG_Compound("hello world") {
+    TAG_String('name'): 'Bananrama'
+}   
+```
+
+To read and write would look like:
+
+```go
+package main
+
+import "bytes"
+import "github.com/Tnze/go-mc/nbt"
+
+type Compound struct {
+    Name string `nbt:"name"` // Note that if name is private (name), the field will not be used
+}
+
+func main() {
+    var out bytes.Buffer
+    banana := Compound{Name: "Bananrama"}
+    _ = nbt.Marshal(&out, banana)
+
+    var rama Compound
+    _ = nbt.Unmarshal(out.Bytes(), &rama)
+}
+```
+
+# Struct field tags
+There are two tags supported:
+- nbt
+- nbt_type
+
+The `nbt` tag is used to change the name of the NBT Tag field, whereas the `nbt_type`
+ tag is used to enforce a certain NBT Tag type when it is ambiguous.
+ 
+For example:
+```go
+type Compound struct {
+    LongArray []int64
+    LongList []int64 `nbt_type:"list"` // forces a long list instead of a long array
+}
+```
+
 # Docs
 [![GoDoc](https://godoc.org/github.com/Tnze/go-mc/nbt?status.svg)](https://godoc.org/github.com/Tnze/go-mc/nbt)