15: Moved Log function to autoload and replace echom

autoload/vue.vim

@@ -0,0 +1,9 @@
+let s:name = 'vim-vue-plugin'
+let s:debug = exists("g:vim_vue_plugin_debug")
+      \ && g:vim_vue_plugin_debug == 1
+
+function! vue#Log(msg)
+  if s:debug
+    echom '['.s:name.']['.v:lnum.'] '.a:msg
+  endif
+endfunction