* set up jest dependencies
* add parser option to eslint to support es6
* migrate first test to jest
* migrate the argv test to shpec
* convert the env and literal store tests
* convert the file-store tests
* convert the memory-store tests
* convert the hierarchy tests
* convert the provider-save test
* convert the complete test
* convert the provider test
* convert the conf test
* tweak a test that was no longer working (context changed)
* replace in place the helpers file
* remove vows dependency
* update the test invocation to rely on jest
* update the argv test to be able to use the jest --verbose option
* Some tweaks to the test to have them working
* Update node version tested (+10 +12 -9)
* Replace const by var until we drop 0.10/0.12/4 node
* Replace let by var until we drop 0.10/0.12/4 node
