Upgrades Mongoose to 4.11.1
Updates Mongoose connection implementation to accommodate deprecated
features & connection options.
Also, updates the Gulp Mocha tasks to reflect changes to the Mongoose
implementation.
Fixes tests to get the database from the existing Mongoose singleton.
Derives from changes in https://github.com/meanjs/mean/pull/1816
Closes https://github.com/meanjs/mean/issues/1814
Adds the ability to configure multiple env configurations, for the
various NODE_ENV's. These configs can be used to override the current
configuration, using the appropriate local-NODE_ENV.js file that the
user has defined.
Updated the local.example.js comments to be clear on the usage.
Added config/env/local-*.js to gitignore.
Updated the copy:localConfig Grunt task to copy local.example as
local-development.js, since we're no longer going to use local.js.
