Triggering only single build when multiple files change at ~same time #32

What currently happens when multiple files are changed at approximately the same time - multiple rake executions are triggered. This is getting quite annoying and actually problematic if the build duration is relatively long.

It would be good to be able to skip the intermediate changes (if there are many on queue) and trigger just a single rake execution. This of course makes sense when no file-specific actions are performed, e.g.:

guard 'rake', :task => 'test' do
    watch(%r{^src/main/.*$})
    watch(%r{^src/test/.*/content\.txt$})
    watch(%r{^setup.*\.sql$})
end