Vim.Buffer: Use 'silent' and 'fnameescape'

fnameescape() is required while tempfile might contains
backslash in Windows.

silent is added while the line is for removing 'tempfile'
from unlisted-buffer which is not a core part of the
function (#439)

Fix lambdalisue/vim-gista#81

autoload/vital/__vital__/Vim/Buffer.vim

@@ -122,7 +122,8 @@ function! s:read_content(content, ...) abort
           \)
   finally
     call delete(tempfile)
-    execute 'bwipeout!' tempfile
+    " To remove 'tempfile' from unlisted-buffer #439
+    silent execute 'bwipeout!' fnameescape(tempfile)
   endtry
 endfunction