Finish HackMyCore reshaping.

Reintroduce HackMyCore, dropping the interim submodule, and reorganize
and improve tests.

src/utils/safe-spawn.coffee

@@ -0,0 +1,28 @@
+###*
+Safe spawn utility for HackMyResume / FluentCV.
+@module utils/safe-spawn
+@license MIT. See LICENSE.md for details.
+###
+
+module.exports = ( cmd, args, isSync, callback ) ->
+
+  try
+
+    # .spawnSync not available on earlier Node.js, so default to .spawn
+    spawn = require('child_process')[ if isSync then 'spawnSync' else 'spawn'];
+    info = spawn cmd, args
+
+    # Check for error depending on whether we're sync or async
+    if !isSync
+      info.on 'error', (err) ->
+        if callback? then callback err; return
+        else throw cmd: cmd, inner: err
+      return
+    else
+      if info.error
+        if callback? then callback err; return
+        else throw cmd: cmd, inner: info.error
+
+  catch
+    if callback? then callback _error
+    else throw _error