Add two extra seconds of data when reading from frame

Because of the way the data is getting cropped, there needs to be an extra two seconds of data read in from the frame file. Modified line 504 in detector.py to reflect this change and load an extra second at the beginning and end of the segment.

tupak/gw/detector.py

@@ -501,7 +501,7 @@ class Interferometer(object):
         elif frame_file is not None:
             logging.info('Reading data from frame, {}.'.format(self.name))
             strain = tupak.gw.utils.read_frame_file(
-                frame_file, t1=epoch, t2=epoch + duration, channel=channel_name, resample=sampling_frequency)
+                frame_file, t1=epoch - 1, t2=epoch + duration + 1, channel=channel_name, resample=sampling_frequency)
             frequency_domain_strain, frequencies = tupak.gw.utils.process_strain_data(strain, **kwargs)
             if overwrite_psd:
                 self.power_spectral_density = PowerSpectralDensity(