[DEV] Encapsulate developer environment with Anaconda

[tallamjr]

To allow for developer contributions, a stand alone environment should be set up using a combination of environment.yml and requirements.txt such as:

# This file may be used to create an environment using:
# $ conda env create --name <env> --file <this file>
# platform: linux-64
name: astroxyz

channels:
  - conda-forge

dependencies:
  - python=3.7

  - pip:
    - -r file:requirements.txt