Here are some functionalities done:
1) Add Donation
2) Listing of Donations
3) Send donation details to the donar
4) Generate individual donation PDF

WIP
1) User with role Center Admin OR Accountant should be able to manage donation for that center
2)
Merge branch 'development' into development_feature_25

Conflicts:
	Gemfile
	Gemfile.lock
	app/views/layouts/_navigation.html.haml
	config/environments/development.rb
	config/locales/en.yml
	config/routes.rb
	config/settings.yml
	db/schema.rb
Remove unnecessary code from en.yml and update version in schema.rb
1) Create user role for "Super Admin" and "Accountant"  from seed.
2) "Super Admin" and "Accountant" can access "Donations" section.
3) Change donation mail content.
4) Change navigation link for "Donations" can access only "Super Admin" and "Accountant"
DIsplay "Received By" in email content, change permissions messages
Add "Center" field in the donation form and display center on mail and PDF
Remove "user_id" from donations table
Manage users role wise - Done
Remove unnecessary gem from gem file
#33 refactored
Merge branch 'development_feature_33' into development

Conflicts:
	Gemfile
	app/controllers/courses_controller.rb
	app/controllers/instructors_controller.rb
	config/locales/en.yml
	config/routes.rb
	db/schema.rb