Add include guard at the beginning of script

No need to re-load the plugin if it has already been loaded. If you have
a specific reason to do so, just do

  ':unlet g:loaded_bracketed_paste'

and then try to reload it.

Signed-off-by: Cihangir Akturk <cakturk@gmail.com>

plugin/bracketed-paste.vim

@@ -9,6 +9,11 @@
 " Docs on mapping fast escape codes in vim
 " http://vim.wikia.com/wiki/Mapping_fast_keycodes_in_terminal_Vim
 
+if exists("g:loaded_bracketed_paste")
+  finish
+endif
+let g:loaded_bracketed_paste = 1
+
 let &t_ti .= "\<Esc>[?2004h"
 let &t_te .= "\<Esc>[?2004l"