Refresh contribution guidelines.
Add upstream / username remotes.  Illustrate rebase.
Used  instead of deprecated function.
median filter outlier
histogram example
Find contours example
Merge pull request #512 from mkcor/doc_fix-deprecationwarning

Used feature.peak_local_max instead of deprecated function
Merge pull request #509 from stefanv/contributor_guidelines

DOC: Refresh contribution guidelines.
Updated Implementation of Roberts Algorithm
Upadated Version with test added(/filter/tests/test_edge.py
ENH: Add `chelsea` to dataset.
Merge pull request #524 from stefanv/chelsea

ENH: Add `chelsea` to dataset.
updated tests for Roberts Edge Detector
BUG: Fix integer type in Felzenwalb cython.
Merge pull request #515 from tonysyu/fix/imread-url-bug

ENH: Fix imread from urls on some backends.
Merge pull request #525 from stefanv/felzenwalb_32

BUG: Fix integer type in Felzenwalb cython.
fix travis complaint
readability
Updated function names[Robert's Edge Detection]
Merge pull request #526 from sciunto/fixtravis