Write `=` into a cell

I had a problem where a user submitted multiple `=` in a text field and exporting the data failed with

```
parse error on value "=" ("=")
/home/ubuntu/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/racc/parser.rb:351:in `on_error'
(eval):3:in `_racc_do_parse_c'
(eval):3:in `do_parse'
```

Is there any way to treat data always as string and skipping the formula parsing?
