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

Merging #25 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #25   +/-   ##
=========================================
  Coverage     92.53%   92.53%           
  Complexity      136      136           
=========================================
  Files             9        9           
  Lines           415      415           
=========================================
  Hits            384      384           
  Misses           31       31

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