Update CONTRIBUTING.md and Travis

[manez]

GitHub Issue: Islandora/documentation#1173 and Islandora/documentation#1175

What does this Pull Request do?

Adds the 'standard' version of CONTRIBUTING.md and add dev branch in travis

How should this be tested?

Look at the .md files and make sure they're good. CONTRIBUTING.md should match this.
Check travis to make sure I've updated correctly, because it's just copied from Islandora/chullo#75 (comment)

Interested parties

Tag (@ mention) interested parties or, if unsure, @Islandora-CLAW/committers

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (dev@c42ca94). Click here to learn what that means.
The diff coverage is n/a.

@@          Coverage Diff           @@
##             dev      #72   +/-   ##
======================================
  Coverage       ?   94.59%           
  Complexity     ?      159           
======================================
  Files          ?        9           
  Lines          ?      647           
  Branches       ?        0           
======================================
  Hits           ?      612           
  Misses         ?       35           
  Partials       ?        0

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