个别概念的错误

[holys]

base.md

index 应该是类似关系型数据库中的 database

An index is like a database in a relational database.

type 才是类似关系型数据库中的 table

A type is like a table in a relational database

参见：https://www.elastic.co/guide/en/elasticsearch/reference/current/glossary.html

[siddontang]

please send me a PR to fix it. Thanks:-)