touch_regex should scan the previous character as well

[savchenko]

An example, in this situation pressing " will create a pair "":

options = {
            disable_when_touch = true*, -- * indicates a cursor
          }

However, in this one disable_when_touch will work as expected and only one " will be inserted:

options = {
            disable_when_touch = *true, -- * indicates a cursor
          }