Add note about python support in README. Related to #54.

README.md

@@ -8,6 +8,9 @@ When no formatprogram exists (or no formatprogram is installed) for a certain fi
 
 How to install
 -----------------------
+It is required that your vim has builtin python support. You can check whether this is the case
+by running `vim --version` and check that `+python` is listed among features.
+
 ####Vundle
 Put this in your .vimrc
 

plugin/autoformat.vim

@@ -113,7 +113,7 @@ function! s:TryFormatter()
 
     if !has("python")
         echohl WarningMsg |
-            \ echomsg "WARNING: vim has no support for python, but it is necessary to verify the custom formatter!" |
+            \ echomsg "WARNING: vim has no support for python, but it is required to run the formatter!" |
             \ echohl None
         return 1
     endif