Tests on Windows: use normalizer for paths

[bastibuck]

Running the tests (or deploy which includes testing) on windows fails due to different path separators.

Also other tests fail on windows. I think most of them are related to path separators. Just copy pasting some test output here:

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Error: ENOENT: no such file or directory, scandir 'C:\dev\appstrap_test_testConfig\config.js\presets'

List of tests throwing this error:

• Presets › Appstrap.reset effects › active presets are removed
• Presets › Appstrap.reset effects › active preset groups are reset
• Presets › Appstrap.reset effects › preloaded presets are not removed

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Error: Unable to load preset file at undefined

List of tests throwing this error:

• Presets › single preset (using loadPreset) › active preset merges onto base response payload
• Presets › single preset (using loadPreset) › active preset replaces base response payload
• Presets › single preset (using loadPreset) › deactivating preset returns base response payload
• Presets › preset composition (using loadPresets) › activating presets with modes of merge <- merge <- merge combine appropriately on base
  -Presets › preset composition (using loadPresets) › activating presets with modes of merge <- replace <- merge result in replace <- merge
• Presets › preset composition (using loadPresets) › activating presets with modes of merge <- merge <- replace result in replace only
• Presets › Preset management via node api › activating a preset updates endpoint behavior as expected

[moffatethan]

I believe you fix this in #31 (comment)