Explicitly mention Instant Client SDK

Author: cjbj

README.md

@@ -46,7 +46,7 @@ Prerequisites:
 
 - [Python 2.7](https://www.python.org/downloads/)
 - C Compiler with support for C++ 11 (Xcode, gcc, Visual Studio or similar)
-- The small, free [Oracle Instant Client](http://www.oracle.com/technetwork/database/features/instant-client/index-100365.html) libraries if your database is remote.  Or use a locally installed database such as the free [Oracle XE](http://www.oracle.com/technetwork/database/database-technologies/express-edition/overview/index.html) release
+- The small, free [Oracle Instant Client](http://www.oracle.com/technetwork/database/features/instant-client/index-100365.html) "basic" and "SDK" packages if your database is remote.  Or use a locally installed database such as the free [Oracle XE](http://www.oracle.com/technetwork/database/database-technologies/express-edition/overview/index.html) release
 - Set `OCI_LIB_DIR` and `OCI_INC_DIR` during installation if the Oracle libraries and headers are in a non-default location
 
 Run `npm install oracledb` to install from the [NPM registry](https://www.npmjs.com/package/oracledb).