Fix module lookup

[daniel-thom]

This PR does two things:

1. Bump the version of Julia to what is actually currently required (1.4).

2. Fixes a bug where deserialization of an InfrastructureSystems type fails if the user has not specifically installed the InfrastructureSystems package.

The user would see an error like this:

ERROR: LoadError: MethodError: no method matching root_module(::Nothing)
Closest candidates are:
  root_module(::Module, ::Symbol) at loading.jl:969
  root_module(::Base.PkgId) at loading.jl:968
Stacktrace:
 [1] root_module(::Module, ::Symbol) at ./loading.jl:969

[codecov[bot]]

Codecov Report

Merging #189 (bc3d059) into master (fdda7ff) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #189      +/-   ##
==========================================
+ Coverage   72.64%   72.65%   +0.01%     
==========================================
  Files          42       42              
  Lines        2643     2644       +1     
==========================================
+ Hits         1920     1921       +1     
  Misses        723      723              

Flag	Coverage Δ
unittests	72.65% <100.00%> (+0.01%)	:arrow_up:

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

Impacted Files	Coverage Δ
src/serialization.jl	44.94% <100.00%> (ø)
src/utils/utils.jl	55.28% <100.00%> (+0.21%)	:arrow_up: