Test and refactoring of RepoSubscriptionsController

  * Add tests for update and destroy actions
  * Replace `where().first` with `find` to avoid errors
    `undefined method destroy for NilClass` when subscription not found
Apply style to pagination

- Ref: http://mislav.uniqpath.com/will_paginate/
Order issues by descending order of created_at
Merge pull request #193 from prathamesh-sonpatki/pagination

Added stylesheet for pagination of issues and Order issues by created_at DESC
Avoid an unnecessary begin/rescue block
Merge pull request #195 from jamescook/james-remove-begin-rescue

Avoid an unnecessary begin/rescue block
Remove wall of text from README [ci skip]

- ALTER ROLE code line looks like it needed formatting
- One less "maintainer" helps increase sentence flow
- Fixes GitHub and URL capitalisation
Merge pull request #196 from randomecho/readme-fix-textwall

Break up wall of text from README
Merge pull request #176 from ck3g/repo-subscriptions-refactoring

Test and refactoring of RepoSubscriptionsController
Fix failing test for RepoSubscription.for

- Removed assertiion with the result of RepoSubscription.for.
- It was returning of ActiveRecord::Relation result which was being
- compared with array
- This method is getting tested from eariler assertion
    `assert_equal [sub1], user.repo_subscriptions_for(repo.id)`