Use monotonic clock for measuring passed time

[ledestin]

Hello,

Capybara uses real clock to measure time which leads to races when clock is moved 1 hour ahead. This pull requests switches Capybara to use monotonic clock, which doesn't have such problems.

I've used a gem (that depends on hitimes) because supported Ruby includes 1.9.3 and monotonic clock is introduced only in Ruby 2.

[twalpole]

Looking at the monotonic_times gem it doesnt seem to provide enough added benefit to justify including it rather than just using hitimes directly. I need to read up on any platform issues that may be involved here, and it may just make more sense to use Process.clock_getTime directly when running on ruby 2.1+

[ledestin]

Your call. I personally think that Process.clock_gettime(Process::CLOCK_MONOTONIC) is way too long to repeat more than a single time.

[twalpole]

Closing in favor of the lesser dependencies (and admittedly lesser platform support) in PR #1503