minor README edit (site update)

README.md

@@ -88,8 +88,8 @@ depending on what suites your needs best.
 You can configure the build, either by editing `config.mk` or else by defining the relevant environment variables 
 prior to invoking `make`. The following build variables can be configured:
 
- - `XCHANGE`: the root of the location where the [Smithsonian/xchange](https://github.com/Smithsonian/xchange) is
-   installed. It expects to find `xchange.h` under `$(XCHANGE)/include` and `libxchange.so` under `$(XCHANGE)/lib`
+ - `XCHANGE`: the root of the location where the [Smithsonian/xchange](https://github.com/Smithsonian/xchange) library 
+   is installed. It expects to find `xchange.h` under `$(XCHANGE)/include` and `libxchange.so` under `$(XCHANGE)/lib`
    or else in the default `LD_LIBRARY_PATH`.
 
  - `CC`: The C compiler to use (default: `gcc`).