Fix ToC

Author: johanbrook

Diff for: README.md

@@ -9,14 +9,14 @@ Usually, building HTML emails yourself is tedious. On top of that, add the need
 3. [Sample app](#sample-app)
 4. [API](#api)
 5. [Usage](#usage)
-   a) [Setting up templates](#setting-up-templates)
-   b) [Template paths on deployed instances](#template-paths-on-deployed-instances)
-   c) [Template helpers](#template-helpers)
-   d) [Layouts](#layouts)
-   e) [Previewing and sending](#previewing-and-sending)
-   f) [Paths](#paths)
-   g) [Sample file structure](#sample-file-structure)
-   e) [Logging](#logging)
+   1. [Setting up templates](#setting-up-templates)
+   2. [Template paths on deployed instances](#template-paths-on-deployed-instances)
+   3. [Template helpers](#template-helpers)
+   4. [Layouts](#layouts)
+   5. [Previewing and sending](#previewing-and-sending)
+   6. [Paths](#paths)
+   7. [Sample file structure](#sample-file-structure)
+   8. [Logging](#logging)
 6. [Version history](#version-history)
 7. [Contributing](#contributing)