ENH: enforced peak_directions to calculate the peaks on the min_max normalizated ODF
BF: corrected tau parameter
TEST: updated test for peak_directions
Corrected peak_extraction script
Updated default peak_values for reconst csd parallel
NF: added function for peak visualization
TEST: added test for fvtk.peaks
DOC: updated CSD example to show the peaks
TEST: tiny cleanup
BF: normalized odf values should be used for search descending as discovered from Bago
RF - fix peak_directions
Merge pull request #18 from MrBago/peak_directions_update

RF - fix peak_directions
TEST: Added tests for peak directions for degerative cases e.g. isotropic, all values very close etc.
TEST: added test which shows the difference of peak_directions with or without using minmax_norm
TEST: added comment on the reason for the high eigenvalue
Added visualization of the response function
DOC: better wording on the CSD example
ENH: the peak_finding will work the same if we don't divide with max-min so we can skip that step to increase speed
DOC: small correction on the example
RF - Make peak finding return zero peaks when there are no good peaks to return