Expand embed option to allow evaluated code

[jessedijkstra]

The embed option works fine if you use true or false as values as they are values by definition, if you however use something like Mix.env == :prod the code is treated as a quoted value which is always truthy resulting in an AST tree:

{:{}, [],
 [:==, [context: DetroitWeb, import: Kernel, line: 6],
  [{:{}, [],
    [{:{}, [],
      [:., [line: 6],
       [{:{}, [],
         [:__aliases__, [alias: false, counter: -576460752303420796, line: 6],
          [:Mix]]}, :env]]}, [line: 6], []]}, :prod]]}

By evaluating the condition things like Mix.env can be used to set the value.

[codecov-io]

Codecov Report

Merging #7 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master     #7   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           2      2           
  Lines          24     25    +1     
=====================================
+ Hits           24     25    +1

Impacted Files	Coverage Δ
lib/ex_css_modules/view.ex	100% <100%> (ø)	⬆️

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[sn3p]

Why break this into two lines?