Gaussian gap calculation

Changed gap calculation to generate gap filter by taking the distance
between the middle 68% of the data (approximately one standard
deviation) as the std of the distribution, assuming that the data is
approximately normally distributed ignoring outliers. Only looking at
the central portion of the data should ignore outliers. Also added
parameter stdGapThresh to be used as the number of standard deviations
from the mean allowable to be classified as gap free. This parameter can
be easily modified for optimization.