README.md in stackprof-0.2.10 vs README.md in stackprof-0.2.11

@@ -316,9 +316,10 @@
 `mode`      | mode of sampling: `:cpu`, `:wall`, `:object`, or `:custom` [c.f.](#sampling)
 `out`       | the target file, which will be overwritten
 `interval`  | mode-relative sample rate [c.f.](#sampling)
 `aggregate` | defaults: `true` - if `false` disables [aggregation](#aggregation)
 `raw`       | defaults `false` - if `true` collects the extra data required by the `--flamegraph` and `--stackcollapse` report types
+`save_every`| (rack middleware only) write the target file after this many requests
 
 ### todo
 
 * file/iseq blacklist
 * restore signal handlers on stop