Documentation: add new section about hosted database (close #150)

Author: alexanderdean

README.md

@@ -2,12 +2,26 @@
 
 Java/Scala: [![Build Status](https://travis-ci.org/snowplow/referer-parser.png)](https://travis-ci.org/snowplow/referer-parser)
 
-referer-parser is a multi-language library for extracting marketing attribution data (such as search terms) from referer URLs, inspired by the [ua-parser] [ua-parser] project (an equivalent library for user agent parsing).
+referer-parser is a database for extracting marketing attribution data (such as search terms) from referer URLs, inspired by the [ua-parser] [ua-parser] project (an equivalent library for user agent parsing).
+
+The referer-parser project also contains multiple libraries for working with the referer-parser database in different languages.
 
 referer-parser is a core component of [Snowplow] [snowplow], the open-source web-scale analytics platform powered by Hadoop and Redshift.
 
 _Note that we always use the original HTTP misspelling of 'referer' (and thus 'referal') in this project - never 'referrer'._
 
+## Database
+
+The latest database is always available on this URL:
+
+https://s3-eu-west-1.amazonaws.com/snowplow-hosted-assets/third-party/referer-parser/referers-latest.yml
+
+The database is updated at most once a month. Each new version of the database is also uploaded with a timestamp:
+
+https://s3-eu-west-1.amazonaws.com/snowplow-hosted-assets/third-party/referer-parser/referers-YYYY-MM.yml
+
+If there is an issue with the database necessitating a re-release within the month, the corresponding files will be overwritten.
+
 ## Maintainers
 
 * Java/Scala: [Snowplow Analytics Ltd] [snowplow-analytics]