Make Context leaner and enable third parties to create them

Contexts are necessary for factories to resolve QSEN into FQSENs based
on partial namespaces and namespace aliases. These provide DocBlocks
with the namespace name and namespace aliases.

The new ContextFactory will enable third parties who don't use
phpDocumentor's Reflection component to construct a Context based on
a class reflector or namespace name (and file contents).

tests/phpDocumentor/Reflection/DocBlock/ContextTest.php

@@ -0,0 +1,61 @@
+<?php
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @copyright 2010-2015 Mike van Riel<[email protected]>
+ * @license   http://www.opensource.org/licenses/mit-license.php MIT
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\DocBlock;
+
+use Mockery as m;
+
+/**
+ * @coversDefaultClass \phpDocumentor\Reflection\DocBlock\Context
+ */
+class ContextTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @covers ::__construct
+     * @covers ::getNamespace
+     */
+    public function testProvidesANormalizedNamespace()
+    {
+        $fixture = new Context('\My\Space');
+        $this->assertSame('My\Space', $fixture->getNamespace());
+    }
+
+    /**
+     * @covers ::__construct
+     * @covers ::getNamespace
+     */
+    public function testInterpretsNamespaceNamedGlobalAsRootNamespace()
+    {
+        $fixture = new Context('global');
+        $this->assertSame('', $fixture->getNamespace());
+    }
+
+    /**
+     * @covers ::__construct
+     * @covers ::getNamespace
+     */
+    public function testInterpretsNamespaceNamedDefaultAsRootNamespace()
+    {
+        $fixture = new Context('default');
+        $this->assertSame('', $fixture->getNamespace());
+    }
+
+    /**
+     * @covers ::__construct
+     * @covers ::getNamespaceAliases
+     */
+    public function testProvidesNormalizedNamespaceAliases()
+    {
+        $fixture = new Context('', ['Space' => '\My\Space']);
+        $this->assertSame(['Space' => 'My\Space'], $fixture->getNamespaceAliases());
+    }
+}