Update Dockerfile to use datajoint/pydev

[eywalker]

Update Dockerfile to base the datajoint image off of the datajoint/pydev instead of the original eywalker/pydev. This reflects planned changes and deviations of eywalker/pydev content from it's current version. Namely, eywalker/pydev will be switched to build up on Ubuntu image rather than the current standard python:3.5 which is ultimately based on a Debian image. datajoint/pydev has been created to be a drop-in replacement of the current eywalker/pydev and will continue to be based on python:3.5 image to maintain compatibility.

[coveralls]

Coverage remained the same at 75.575% when pulling 2d90a8f on eywalker:master into ee3e7dd on datajoint:master.