Unit tests and I/O bindings (#8)

* Added composer config, added IO/error tests using phpunit

* Added ApiGen doc comments

* Added test to ensure last_error is not set from loading up the CRT

lib/tests/ErrorTest.php

@@ -0,0 +1,26 @@
+<?php
+
+require_once('tests.inc');
+
+final class ErrorTest extends PHPUnit_Framework_TestCase {
+    private static $crt = null;
+    public static function setUpBeforeClass() {
+        self::$crt = new CRT();
+    }
+
+    public static function tearDownAfterClass() {
+        self::$crt = null;
+    }
+
+    public function testNoInitialError() {
+        $this->assertEquals(0, CRT::last_error());
+    }
+
+    public function testCanResolveErrorName() {
+        $this->assertEquals("AWS_ERROR_SUCCESS", CRT::error_name(0));
+    }
+
+    public function testCanResolveErrorStr() {
+        $this->assertEquals("Success.", CRT::error_str(0));
+    }
+}