Laravel 5.6 updates

Travis config update

Removed HHVM script as Laravel no longer support HHVM after releasing 5.3

vendor/symfony/process/ProcessUtils.php

@@ -29,55 +29,6 @@ class ProcessUtils
     {
     }
 
-    /**
-     * Escapes a string to be used as a shell argument.
-     *
-     * @param string $argument The argument that will be escaped
-     *
-     * @return string The escaped argument
-     *
-     * @deprecated since version 3.3, to be removed in 4.0. Use a command line array or give env vars to the `Process::start/run()` method instead.
-     */
-    public static function escapeArgument($argument)
-    {
-        @trigger_error('The '.__METHOD__.'() method is deprecated since Symfony 3.3 and will be removed in 4.0. Use a command line array or give env vars to the Process::start/run() method instead.', E_USER_DEPRECATED);
-
-        //Fix for PHP bug #43784 escapeshellarg removes % from given string
-        //Fix for PHP bug #49446 escapeshellarg doesn't work on Windows
-        //@see https://bugs.php.net/bug.php?id=43784
-        //@see https://bugs.php.net/bug.php?id=49446
-        if ('\\' === \DIRECTORY_SEPARATOR) {
-            if ('' === $argument) {
-                return escapeshellarg($argument);
-            }
-
-            $escapedArgument = '';
-            $quote = false;
-            foreach (preg_split('/(")/', $argument, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE) as $part) {
-                if ('"' === $part) {
-                    $escapedArgument .= '\\"';
-                } elseif (self::isSurroundedBy($part, '%')) {
-                    // Avoid environment variable expansion
-                    $escapedArgument .= '^%"'.substr($part, 1, -1).'"^%';
-                } else {
-                    // escape trailing backslash
-                    if ('\\' === substr($part, -1)) {
-                        $part .= '\\';
-                    }
-                    $quote = true;
-                    $escapedArgument .= $part;
-                }
-            }
-            if ($quote) {
-                $escapedArgument = '"'.$escapedArgument.'"';
-            }
-
-            return $escapedArgument;
-        }
-
-        return "'".str_replace("'", "'\\''", $argument)."'";
-    }
-
     /**
      * Validates and normalizes a Process input.
      *
@@ -115,9 +66,4 @@ class ProcessUtils
 
         return $input;
     }
-
-    private static function isSurroundedBy($arg, $char)
-    {
-        return 2 < \strlen($arg) && $char === $arg[0] && $char === $arg[\strlen($arg) - 1];
-    }
 }