Billy/764 flash white start

[okwme]

Closes #764
(also closes #502)

Description: Theme styles weren't being applied before electron was launching. Show has beed set to false until the ready-to-show event has fired. Furthermore 300ms have been added for the icons font to load (at 250ms they were still not loaded). The mock electron app has been updated with the new event listener for tests.

Realized vue-resource was not being used even though included and causing the Critical dependency warning so it was removed as well : )

[codecov]

Codecov Report

Merging #875 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #875   +/-   ##
========================================
  Coverage    89.37%   89.37%           
========================================
  Files           96       96           
  Lines         1723     1723           
  Branches        97       97           
========================================
  Hits          1540     1540           
  Misses         167      167           
  Partials        16       16

Impacted Files	Coverage Δ
app/src/renderer/main.js	94.11% <ø> (ø)	⬆️
app/src/main/index.js	100% <ø> (ø)	⬆️