Updated Guardfile template so that Guard can watch the new rails helper file.

rspec-rails v3.0.0 generate the new rails helper file.

[rspec-rails Changelog.md#300--2014-06-01](https://github.com/rspec/rspec-rails/blob/master/Changelog.md#300--2014-06-01)
> Separate RSpec configuration in generated spec_helper from Rails setup and associated configuration options. Moving Rails specific settings and options to rails_helper. (Aaron Kromer)

Updated Guardfile template so that Guard can watch it.