Update README.md

Author: sksamuel

README.md

@@ -50,7 +50,7 @@ regular expressions.
 
 Example:
 ```scala
-ScoverageSbtPlugin.ScoverageKeys.coverageExcludedPackages := "<empty>;Reverse.*;.*AuthService.*;models\.data\..*"
+ScoverageSbtPlugin.ScoverageKeys.coverageExcludedPackages := "<empty>;Reverse.*;.*AuthService.*;models\\.data\\..*"
 ```
 
 The regular expressions are matched against the fully qualified class name, and must match the entire string to take effect.