Update References to latest stable versions

[brianpopow]

Prerequisites

• [x] I have written a descriptive pull-request title
• [x] I have verified that there are no overlapping pull-requests open
• [x] I have verified that I am following matches the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules :cop:.
• [x] I have provided test coverage for my change (where applicable)

Description

This PR updates ImageSharp reference to 1.0.4 and other external dependencies to latest stable versions.

[codecov[bot]]

Codecov Report

Merging #168 (f033d7d) into master (d617c40) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #168   +/-   ##
=======================================
  Coverage   70.03%   70.03%           
=======================================
  Files          89       89           
  Lines        5209     5209           
  Branches     1062     1062           
=======================================
  Hits         3648     3648           
  Misses       1347     1347           
  Partials      214      214           

Flag	Coverage Δ
unittests	70.03% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...geSharp.Drawing/Shapes/EllipticalArcLineSegment.cs	85.45% <ø> (ø)

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