Fix typo in Error handling controller code

On the frontend, the error message 'Username already exist' appears when creating a user with the same username as an existing user.  Grammatically, this error looks strange.  A more proper error message would be 'Username already exists'.  Possibly later on support can be added to properly conjugate this error message for a 'plural' field.
Genericize invalid username or password message

https://github.com/meanjs/mean/issues/133
The message given to the user upon an invalid login attempt, for security reasons, should not reveal that the username or password was incorrect.  Rather, a generic message should be displayed when the username or password is incorrect.
adding https option for running with TLS/SSL
Remove redundant variable declaration
adding secure.js environment option, reverting production.js, and adding openssl options to gen-certs
Rise gunt-concurrent task limit.

Fixes issue with default value for grunt-concurrent limit in machines with few cpu/cores.

From grunt-concurrent docs:

	limit

	Type: Number
	Default: Number of CPU cores (require('os').cpus().length) with a minimum of 2

	Limit of how many tasks that are run concurrently.

In machines with few cpus/cores, the default limit of 2 the 'grunt debug' task
can't start enough tasks for starting the node-inspector task, so the command fails
and the capp can't be debugged.

Fixes issue #144
Fixed typo of div attribute
moving security configs to secure code block to remove requirement for private key and certificate
Removed localhost from env files, as it is not necesary and can introduce bugs in non-local environments.
Use ng-annotate instead of ngmin
Feature: Article CRUD ops. Added supertests. closes meanjs/mean#92
Tiny fixes

Removed double requires and unused variables.
Merge pull request #132 from macsj200/patch-1

Fix typo in Error handling controller code
Merge pull request #139 from macsj200/patch-2

Genericize invalid username or password message
Merge pull request #141 from NeverOddOrEven/remove-redundant-variable-declaration

Remove redundant variable declaration
Merge pull request #156 from miguelcoba/issue-144

Rise gunt-concurrent task limit.
Merge pull request #165 from neon5/master

Fixed typo of div attribute
Merge pull request #197 from Nepoxx/patch-4

Tiny fixes
Merge branch 'pr/177'
Small Update