Updated to laravel 5.5

Closes #590

app/Http/Middleware/EncryptCookies.php

@@ -2,9 +2,9 @@
 
 namespace BookStack\Http\Middleware;
 
-use Illuminate\Cookie\Middleware\EncryptCookies as BaseEncrypter;
+use Illuminate\Cookie\Middleware\EncryptCookies as Middleware;
 
-class EncryptCookies extends BaseEncrypter
+class EncryptCookies extends Middleware
 {
     /**
      * The names of the cookies that should not be encrypted.

app/Http/Middleware/TrimStrings.php

@@ -2,9 +2,9 @@
 
 namespace BookStack\Http\Middleware;
 
-use Illuminate\Foundation\Http\Middleware\TrimStrings as BaseTrimmer;
+use Illuminate\Foundation\Http\Middleware\TrimStrings as Middleware;
 
-class TrimStrings extends BaseTrimmer
+class TrimStrings extends Middleware
 {
     /**
      * The names of the attributes that should not be trimmed.

app/Http/Middleware/TrustProxies.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace BookStack\Http\Middleware;
+
+use Illuminate\Http\Request;
+use Fideloper\Proxy\TrustProxies as Middleware;
+
+class TrustProxies extends Middleware
+{
+    /**
+     * The trusted proxies for this application.
+     *
+     * @var array
+     */
+    protected $proxies;
+
+    /**
+     * The current proxy header mappings.
+     *
+     * @var array
+     */
+    protected $headers = [
+        Request::HEADER_FORWARDED => 'FORWARDED',
+        Request::HEADER_X_FORWARDED_FOR => 'X_FORWARDED_FOR',
+        Request::HEADER_X_FORWARDED_HOST => 'X_FORWARDED_HOST',
+        Request::HEADER_X_FORWARDED_PORT => 'X_FORWARDED_PORT',
+        Request::HEADER_X_FORWARDED_PROTO => 'X_FORWARDED_PROTO',
+    ];
+}

app/Http/Middleware/VerifyCsrfToken.php

@@ -2,9 +2,9 @@
 
 namespace BookStack\Http\Middleware;
 
-use Illuminate\Foundation\Http\Middleware\VerifyCsrfToken as BaseVerifier;
+use Illuminate\Foundation\Http\Middleware\VerifyCsrfToken as Middleware;
 
-class VerifyCsrfToken extends BaseVerifier
+class VerifyCsrfToken extends Middleware
 {
     /**
      * The URIs that should be excluded from CSRF verification.