Remove xdiff code, xdiff does not treat conflicts well.

Author: bircher

.travis.yml

@@ -10,6 +10,5 @@ php:
 
 before_script:
   - git --version
-  - pecl install xdiff
   - composer install --prefer-dist --dev
 

composer.json

@@ -1,8 +1,8 @@
 {
     "name": "bircher/php-merge",
     "type": "library",
-    "description": "A PHP merge utility using the Diff php library, the command line git or xdiff.",
-    "keywords": ["git", "merge", "xdiff"],
+    "description": "A PHP merge utility using the Diff php library or the command line git.",
+    "keywords": ["git", "merge"],
     "homepage": "https://github.com/bircher/php-merge",
     "license": "MIT",
     "authors": [