Adjust README headings to avoid duplicate H1

README.md

@@ -7,13 +7,12 @@ View git diff in Vim tabs.
 - `GitDiff`, `GitDiffInfo`, `GitDiffOff` commands for Vim.
 
 
-Install
-=======
+## Install
 
 Install like general Vim plugins.
 
 
-## Install Zsh Helper Function
+### Install Zsh Helper Function
 
 - With [zcomet][]
 
@@ -39,8 +38,7 @@ Install like general Vim plugins.
   ```
 
 
-Zsh Function Usage
-==================
+## Zsh Function Usage
 
 In zsh, use `gitdiffall` to open git diff in Vim tabs, examples:
 
@@ -64,8 +62,7 @@ For convenience, some special notations are available:
 During merge conflicts, `gitdiffall` will open a 3-way diff in Vim.
 
 
-Zsh Function Configuration
-==========================
+## Zsh Function Configuration
 
 gitdiffall.rb takes configure file from one of the following:
 
@@ -101,8 +98,7 @@ CONFIG = {
 ```
 
 
-Tips
-====
+## Tips
 
 In tmux copy mode, select some commit hash and press `>` to do gitdiffall in
 new tmux window, see [tmux-in.rb][] gist.