Fix compatibility with Rails 4 browser error reporting

Rails 4 has introduced a new way of code extraction for browser error
reporting (https://github.com/rails/rails/blob/fe12e4650802d8f28136660fc9ce62c6a28f19e1/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb#L59).

If a syntax error occurred in template, we should prepend to the
backtrace template's filename and line.

Without it, we'll get an useless 500 error with ```We're sorry but something went wrong``` message.

With fix:
![2014-08-03 13 44 53](https://cloud.githubusercontent.com/assets/4391269/3790239/e1fd628e-1af2-11e4-94a0-a0dc5657f86a.png)

Also, extend syntax error tests to the introduced case.