Improved UPGRADE.md file

Author: norberttech

UPGRADE.md

@@ -1,26 +1,24 @@
 # 3.x -> 4.0 
 
-Below you can find list of changes between 3.x and 4.0 versions of PHPMatcher.
-
-### Creating Matcher
+Below you can find list of changes between `3.x` and `4.0` versions of PHPMatcher.
 
+**Creating Matcher:** 
 ```diff
 -$factory = new MatcherFactory();
--$this->matcher = $factory->createMatcher();
-```
-
-```diff
-+$this->matcher = new PHPMatcher();
+-$matcher = $factory->createMatcher();
++$matcher = new PHPMatcher();
 ```
 
-### Simple Matching
-
+**Using Matcher**
 ```diff
 -PHPMatcher::match($value, $pattern, $error)
++$matcher = (new PHPMatcher())->match($value, $pattern);;
 ```
 
+**Accessing last error/backtrace**
 ```diff
 +$matcher = new PHPMatcher();
 +$matcher->match($value, $pattern);
 +echo $matcher->error();
++echo $matcher->backtrace();
 ```