Fix deep-merge for edn files

[brenopanzolini]

• Please check if the PR fulfills these requirements

• There is an open issue describing the problem that this pr intents to solve.
  • You have a descriptive commit message with a short title (first line).
• Tests for the changes have been added (for bug fixes / features).
• Docs have been added / updated (for bug fixes / features).

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

This PR fixes a bug in the function that checks if a file path ends with .edn which is used to decide if the file will be merged.

The actual function has its arguments reversed:

#(.endsWith ".edn" (.getPath ^File %)) ;; Current
#(.endsWith (.getPath ^File %) ".edn") ;; New

• What is the current behavior?
  The .edn files are not deep-merged during the build due to a bug in the function that checks if the file path ends with .edn.

• What is the new behavior (if this is a feature change)?
  Not a new behavior, just fixing the logic to deep-merge .edn files.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  No breaking changes.

• Other information:
  Relates with: The deep-merge functionality for .edn files doesn't work #35

[brenopanzolini]

Hash sets are merged too.

(def left #{1 2})
(def right #{1 3})
(into left right)
;; => #{1 3 2}

[hlship]

This mistake I made, the actual bug, was that nothing exercised the base rules. It should be possible to have two copies of the same file on the classpath by introducing a second test resources route. Alternately, the rules could be unit tested seperate from the reading-and-merging logic.