feat(namespace): Official support overriding the default namespace

use opts.namespace instead opts._namespace

 add documentation to
opts.namespace

BREAKING CHANGE: undocumented opts._namespace won't work anymore

Closes hypercore-protocol#2

README.md

@@ -27,12 +27,22 @@ Create a new Corestore instance.
 
 `storage` can be either a random-access-storage module, a string, or a function that takes a path and returns an random-access-storage instance.
 
-#### `const core = store.get(key | { name: 'a-name', ...hypercoreOpts})`
-Loads a Hypercore, either by name (if the `name` option is provided), or from the provided key (if the first argument is a Buffer, or if the `key` options is set).
+#### `const core = store.get(key | options)`
+Loads a Hypercore, either by name (if the `name` option is provided), or from the provided key (if the first argument is a Buffer, or if the `key` option is set).
+
+`options` include:
+
+``` js
+{
+  name: 'a-name', // name to derive the Hypercore keyPair from
+  key: key, // or pass the public key of a non-writable Hypercore
+  ...hypercoreOpt
+}
+```
 
 If that Hypercore has previously been loaded, subsequent calls to `get` will return a new Hypercore session on the existing core.
 
-All other options besides `name` and `key` will be forwarded to the Hypercore constructor.
+All other options besides `name`, `key`, `namespace` will be forwarded to the Hypercore constructor.
 
 #### `const stream = store.replicate(opts)`
 Creates a replication stream that's capable of replicating all Hypercores that are managed by the Corestore, assuming the remote peer has the correct capabilities.

index.js

@@ -25,7 +25,7 @@ module.exports = class Corestore extends EventEmitter {
 
     this._keyStorage = null
     this._primaryKey = opts.primaryKey
-    this._namespace = opts._namespace || DEFAULT_NAMESPACE
+    this._namespace = opts.namespace || DEFAULT_NAMESPACE
     this._replicationStreams = opts._streams || []
     this._overwrite = opts.overwrite === true
 
@@ -277,7 +277,7 @@ module.exports = class Corestore extends EventEmitter {
   namespace (name) {
     if (!b4a.isBuffer(name)) name = b4a.from(name)
     return new Corestore(this.storage, {
-      _namespace: generateNamespace(this._namespace, name),
+      namespace: generateNamespace(this._namespace, name),
       _opening: this._opening,
       _cores: this.cores,
       _streams: this._replicationStreams,