Prefer g:php_cs_fixer_path if set, even if php-cs-fixer is executable

Fixes #32

Author: Rocka84

autoload/php_cs_fixer.vim

@@ -6,12 +6,17 @@
 let g:php_cs_fixer_path = get(g:, 'php_cs_fixer_path', '~/php-cs-fixer.phar')
 let g:php_cs_fixer_php_path = get(g:, 'php_cs_fixer_php_path', 'php')
 
-if executable('php-cs-fixer')
-  let g:php_cs_fixer_command = 'php-cs-fixer fix'
-  let g:php_cs_fixer_version_command = 'php-cs-fixer --version'
-else
+if exists('g:php_cs_fixer_path')
   let g:php_cs_fixer_command = g:php_cs_fixer_php_path.' '.g:php_cs_fixer_path.' fix'
   let g:php_cs_fixer_version_command = g:php_cs_fixer_php_path.' '.g:php_cs_fixer_path.' --version'
+else
+  if executable('php-cs-fixer')
+    let g:php_cs_fixer_command = 'php-cs-fixer fix'
+    let g:php_cs_fixer_version_command = 'php-cs-fixer --version'
+  else
+    echoerr('php-cs-fixer not found and g:php_cs_fixer_path not set')
+    finish
+  end
 end
 
 " Check the php-cs-fixer version