Update ReadMe.txt to reflect updated ZIP/download process on github.com.

ReadMe.txt

@@ -15,12 +15,11 @@ button in the main loop, which should execute as fast as possible.
 
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 To use the library:
-(1) Go to https://github.com/JChristensen/Button/downloads and download the
-file in the compressed format of your choice (zip or tar.gz) to a convenient
-location on your PC.
+(1) Go to https://github.com/JChristensen/Button and click the ZIP button to
+download the repository as a ZIP file to a convenient location on your PC.
 (2) Uncompress the downloaded file. This will result in a folder containing all
-the files for the library, that has a name similar to "JChristensen-
-Button-42e98a7".
+the files for the library, that has a name that includes the branch name,
+for example "Button-master".
 (3) Rename the folder to just "Button".
 (4) Copy the renamed folder to the Arduino sketchbook\libraries folder.