Add README to tig plugin

plugins/tig/README.md

+# `tig` plugin
+
+This plugin adds some aliases for people who work with `tig` in
+a regular basis. To use it, add `tig` to your plugins array:
+
+```zsh
+plugins=(... tig)
+```
+
+## Features
+
+| Alias | Command        | Description                                     |
+|-------|----------------|-------------------------------------------------|
+| `tis` | `tig status`   | Show git status                                 |
+| `til` | `tig log`      | Show git log                                    |
+| `tib` | `tig blame -C` | `git-blame` a file detecting copies and renames |

plugins/tig/tig.plugin.zsh

 alias tis='tig status'
 alias til='tig log'
-
-# blame a single file and list commits
 alias tib='tig blame -C'
-