Merge pull request #2 from rproepp/master

Fix new RateEstimator and gitignore
safety commit
refractory period spike prior bias
robert addressing the div-by-zero error in the rate estimation
tests moved back into botmpy package, xi_vs_f bug fixed,
still wont work for even tf
additional spike detections without deletions
Merge pull request #5 from greendev1l/master

SDPeakNode in nodes/spike_detection.py
* covariance estimator from concatenated matric factory
* initialisation loader from spykeviewer
* verbosity fine tuning
Bugfix: Exception in RateEstimator when there are no samples (sample_size==0)