Update Readme as LOB types are already supported

As per chat discussion on https://gitter.im/R2DBC/r2dbc#, Mark Paluch @mp911de mentioned that support is already present, but readme is not updated

[closes #493]

Signed-off-by: Mark Paluch <mpaluch@vmware.com>

README.md

@@ -15,7 +15,7 @@ This driver provides the following features:
 * Binary data transfer
 * Execution of prepared statements with bindings
 * Execution of batch statements without bindings
-* Read and write support for all data types except LOB types (e.g. `BLOB`, `CLOB`)
+* Read and write support for a majority of data types (see [Data Type Mapping](#data-type-mapping) for details)
 * Fetching of `REFCURSOR` using `io.r2dbc.postgresql.api.RefCursor`
 * Extension points to register `Codec`s to handle additional PostgreSQL data types