Newsletters feature implemented.

[dhruvhacks]

This PR adds-

• Views to access Newsletters of various departments.
• Access to specific groups to add new Newsletters.
• Templates for newsletters section.

closes #229

@RishabhJain2018 please review 🙂

[dhruvhacks]

To cover the build failures, #231 must be merged first.

[RishabhJain2018]

@dhruvhacks Please add the newsletter models along with the migration files in a separate PR.

[dhruvhacks]

@RishabhJain2018 Okay sir.

[dhruvhacks]

@RishabhJain2018 Please review #233. It contains the models and migration files of this feature.

[RishabhJain2018]

@dhruvhacks Please add the screenshots of the UI.

[dhruvhacks]

@RishabhJain2018
Sure sir! Here are the screenshots of the UI-

1. Newsletters link will be available left menu.
   

2. This link will redirect to a page which lists all the departments. This will be a open link. But for a logged in user, if they are among the authorized groups, they will get a 'Add new' button-
   

3. Selecting a menu will list all the newsletters uploaded by that department. If no newsletter found, page will display 'No newsletter Found'
   
   

4. For an authorized member, a form will be provided for uploading newsletters-
   

[dhruvhacks]

@RishabhJain2018 Sir please do not merge this PR before merging #233 into this branch. This way complete feature can be tested once. Target of #233 is already set to this branch.

[RishabhJain2018]

@dhruvhacks Feel free to merge this as well as per your plan.

[dhruvhacks]

@RishabhJain2018 Okay sir! Since this PR is stale, will update it and consider merging!