README: add version when feature was introduced.

For a few things that were added recently.

README.md

@@ -225,8 +225,8 @@ stdout and stderr output:
 
 * The stdout produced by the script must only contain the `test2json` output, or
   `gotestsum` will fail. If it isn't possible to change the script to avoid
-  non-JSON output, you can use `--ignore-non-json-output-lines` to ignore
-  non-JSON lines and write them to `gotestsum`'s stderr instead.
+  non-JSON output, you can use `--ignore-non-json-output-lines` (added in version 1.7.0)
+  to ignore non-JSON lines and write them to `gotestsum`'s stderr instead.
 * Any stderr produced by the script will be considered an error (this behaviour
   is necessary because package build errors are only reported by writting to
   stderr, not the `test2json` stdout). Any stderr produced by tests is not
@@ -334,15 +334,19 @@ directory will be watched. Use the `--packages` flag to specify a different list
 While in watch mode, pressing some keys will perform an action:
 
 * `r` will run tests for the previous event.
+  Added in version 1.6.1.
 * `d` will run tests for the previous event using `dlv test`, allowing you to 
   debug a test failure using [delve]. A breakpoint will automatically be added at
   the first line of any tests which failed in the previous run. Additional
   breakpoints can be added with [`runtime.Breakpoint`](https://golang.org/pkg/runtime/#Breakpoint)
   or by using the delve command prompt.
+  Added in version 1.6.1.
 * `a` will run tests for all packages, by using `./...` as the package selector.
+  Added in version 1.7.0.
 * `l` will scan the directory list again, and if there are any new directories
   which contain a file with a `.go` extension, they will be added to the watch
   list.
+  Added in version 1.7.0.
 
 Note that [delve] must be installed in order to use debug (`d`).