Add Apache Spark

See: https://github.com/sindresorhus/awesome/pull/895#issuecomment-303697626

readme.md

@@ -266,6 +266,7 @@
 - [Hadoop](https://github.com/youngwookim/awesome-hadoop) - Framework for distributed storage and processing of very large data sets.
 - [Data Engineering](https://github.com/igorbarinov/awesome-data-engineering)
 - [Streaming](https://github.com/manuzhang/awesome-streaming)
+- [Apache Spark](https://github.com/awesome-spark/awesome-spark) - Unified engine for large-scale data processing.
 
 
 ## Theory