Adds method to set values in DEFAULT_OPTS

Fix for #488 Override DEFAULT_OPTS 

I think it would be better to unfreeze `DEFAULT_OPTS`.

### Usage

```
### support/01_launch.rb

...
require 'calabash-cucumber/wait_helpers'

Before do |scenario|
  Calabash::Cucumber::WaitHelpers.override_default_option(:timeout, 1)
  ...
end
```