Merge pull request #274 from Garyfallidis/peak_directions_update

Peak directions update
Merge pull request #4 from Garyfallidis/segfault_issue

BF: added check for when seeds are out of volume's boundaries
Merge pull request #285 from MrBago/segfault_issue

Bad seeds cause segfault in EuDX
NF: often it makes long time forall the examples to run and that makes debugging examples cumbersome. This update allows to define which examples can be run by commenting a file in the examples folder named valid_examples.txt
DOC: updated examples index rst
BF: added try catch for when SVD doesn't converge inside the CSD iteration loop
NF: adding quick start example ...
DOC: updated documentation of parallel example which was off topic
A bit better restructured text than before
working on the wording of the snr_cc example
cleaning up and simplifying snr example and cc segmentation
cleaning up and simplifying snr example and cc segmentation
snr_in_cc done cleaning
cleaning up cc_segmentation example
wip
DOC: new example for real beginners who don't know much about data analysis in python and they want to start using Dipy
DOC: corrected some language mistakes and typos
DOC: minor correction
correcting typos
correcting typos