HTTP: move utils to a proper file, add tests

Relates to #333

Modifications:
 - move HTTP utils to 'application/HttpUtils.php'
 - simplify logic
   - replace 'http_parse_headers_shaarli' by built-in 'get_headers()'
   - remove superfluous '$status' parameter (provided by the HTTP headers)
 - apply coding conventions
 - add test coverage (unitary only)

Signed-off-by: VirtualTam <virtualtam@flibidi.net>

tests/HttpUtilsTest.php

@@ -0,0 +1,38 @@
+<?php
+/**
+ * HttpUtils' tests
+ */
+
+require_once 'application/HttpUtils.php';
+
+/**
+ * Unitary tests for get_http_url()
+ */
+class GetHttpUrlTest extends PHPUnit_Framework_TestCase
+{
+    /**
+     * Get an invalid local URL
+     */
+    public function testGetInvalidLocalUrl()
+    {
+        list($headers, $content) = get_http_url('/non/existent', 1);
+        $this->assertEquals('HTTP Error', $headers[0]);
+        $this->assertRegexp(
+            '/failed to open stream: No such file or directory/',
+            $content
+        );
+    }
+
+    /**
+     * Get an invalid remote URL
+     */
+    public function testGetInvalidRemoteUrl()
+    {
+        list($headers, $content) = get_http_url('http://non.existent', 1);
+        $this->assertEquals('HTTP Error', $headers[0]);
+        $this->assertRegexp(
+            '/Name or service not known/',
+            $content
+        );
+    }
+}