Add price field for each mixture. Closes #39.

* Add currency application.
* Add USD price field in mixture model.
* Add templatetag to convert currency value in template rendering.
* Add test for templatetag.
* Add default currency code to convert prices.
Merge branch 'feature-39-Add_price_value_for_products' into release-6
Add price field on mixture.
Merge branch 'develop' into release-6. Refs #39.

Conflicts:
	poppurri/mixture/models.py
Merge branch 'release-6' into develop
Add manager command to update currency values. Closes #41.

* Add command 'update_currencies' to fetch API values.
* Add test units for command behaviour.
* Add base settings for currency application.
Merge branch 'enhancement-41-Use_API_to_update_currency_values' into develop
Change URL format for mixtured and category details. Closes #36.

* Change URL format for mixture detail to /mixture/id/slug/.
* Change URL format for category detail to /category/id/slug/.
Merge branch 'enhancement-36-Change_mixture_detail_URL_format' into develop
Customize admin console templates. Closes #34.

* Change to project name as admin console title.
* Add Rosetta application link in admin and back to home.
Merge branch 'enhancement-34-Customize_admin_templates' into develop
Add carousel for images on mixture detail. Closes #30.
Merge branch 'feature-30-Add_carousel_for_pictures_on_mixture_detail' into develop
Merge branch 'develop' into release-6
Change price text if mixture's price is not defined.
Fix return data type on templatetag.
Merge branch 'release-6' into develop
Add sentry configuration for each environment.
Add restart + update currencies on deploy.
Add initial data for currencies application.