Speed up the timing reconstructions

ProcessEventsWithTriggerOffset is faster in most cases.
Sometimes even 8x as fast!

Use generators for the traces.
Not required to convert the entire traces to ints and an array.
Go through the traces only once.

Still needs logic if adc_threshold > ADC_LOW_THRESHOLD

And tests..
Cleanup ProcessEventsWithTriggerOffset

Fix PEP8 violations!
Breaks some parts into functions
Again checked: same results as old method
Add tests for new methods

Fix some broken tests
Make some functions class/static methods.
Makes them easier to test.
Fix skipIf for ProcessEventsTests

Now checks the correct path for the file existence
Merge pull request #28 from HiSPARC/process_events_generator

Speed up the timing reconstructions
Use generators for the traces
Don't go through entire traces if there is nothing to find (baseline + pulseheight)