Ensure build fails when we have spec failures.

SystemExit was being swallowed by our `ensure` block in
capture_warnings.
Work around for JRuby

Planning to move this into Gherin#rubify so that we don't have to deal
with it here.
Use less specific version of coveralls.
Revert "Work around for JRuby"

This reverts commit 6596fedbe9007345fea1e604a09cee4e512f9d86.
Ensure multiline arg location matching works in JRuby
Use `Set` for locations.

Get's rid of the strange module as an abstract class pattern.

Hat-tip to @jdks
Fix a couple of bugs needed for
https://github.com/cucumber/cucumber/pull/590
Fix #37

Look mum, no tests! =:O
Maintain the backtrace when we add duration to Pending exception
NameFilter added
debug output removed
Add LocationFilter from front-end

And move all filters into a single file.
Fix build
Match location of empty scenarios

Ref (cucumber/cucumber#601)
Print keyword in test case name

This helps to fix a couple of scenarios in the front-end