feat/Add support for Model.insertMany

[RAYDENFilipp]

The plugin didn't support pre-hook for insertMany event, so it has been added.

Colses the issue #23 .

Changes include:

• Add new pre-hook insertMany
  • add processDocumentsOnInsertMany function and its tests for better coverage
  • processDocumentsOnInsertMany does the vary same as a callback, passed to post-save hook with the only difference that it receives document-objects array and getting/setting fields is performed on each document and next is called only if the last document has been processed.
• Change mocha/should/nyc pack with jest to allow for a set of similar test suites, like describe.each, it.each.
• Since insertMany should be tested with an array of documents, but tests would be the same as with testing new Model, the following has been made:
  • Two suites of test cases were created: 'create document with "new Model"' and 'create documents with "Model.insertMany"'
  • For each suite its own function-creator has been made, createDocumentWithNewModel & createDocumentsWithInsertMany, each receiving an array of docs with a difference that createDocumentWithNewModel also receiving an array, but only one document from there will be processed. Array of documents is used in both suites to allow describe.each to properly work.
  • Efforts have been made to adhere to the code style (use of vars, function declarations instead of expressions/arrow functions);

P.S. another good idea to unite both hooks would have been to use validate since it triggered in both cases.

If this PR still seems too hard to follow along, it is possible to discuss over Skype, Whatsapp, or anything similar.

[proswdev]

Hi RAYDENFilipp. Sorry for the late response would be a bit of an understatement ;-) I would like to include your PR but not ready to move the testing framework over to jest for various internal reasons. If you're still willing and able to include the PR, could you please switch testing back to mocha? Thx, Eric