Add honza snippets function for compatibility

autoload/vim_snippets.vim

@@ -0,0 +1,11 @@
+" For honza-snippets function.
+function! vim_snippets#Filename(...)
+  let filename = expand('%:t:r')
+  if filename == ''
+    return a:0 == 2 ? a:2 : ''
+  elseif a:0 == 0 || a:1 == ''
+    return filename
+  else
+    return substitute(a:1, '$1', filename, 'g')
+  endif
+endfunction