Bump version to 0.5.0.

[dsjen]

@edx/educator-dahlia

[codecov-io]

Codecov Report

Merging #65 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #65   +/-   ##
======================================
  Coverage    62.5%   62.5%           
======================================
  Files          20      20           
  Lines         312     312           
  Branches       45      45           
======================================
  Hits          195     195           
  Misses        113     113           
  Partials        4       4

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bb9e251...3d3685a. Read the comment docs.