Merge pull request rust-lang#3019 from yangby-cryptape/fix-typo-in-readme

Fix typo in README.md.

Author: topecongiro

README.md

@@ -189,15 +189,15 @@ See [Configurations.md](Configurations.md) for details.
   Example:
 
   ```
-  cargo fmt --emit files
+  cargo fmt -- --emit files
   ```
 
   Options:
 
   | Flag |Description| Nightly Only |
   |:---:|:---:|:---:|
   | files | overwrites output to files | No |
-  | stdout | writes output to stdout | No | 
+  | stdout | writes output to stdout | No |
   | coverage | displays how much of the input file was processed | Yes |
   | checkstyle | emits in a checkstyle format | Yes |