readme: convert to markdown in root dir

README.md

@@ -1,14 +1,13 @@
+# shunt-tags
+
 Script to rename filenames in a certain way.
 
 `shunt_tags` shunt tags to the end of filenames, transforming `[RELEASEGROUP] Title - Episode [CRC32].mkv` into `Title - Episode [RELEASEGROUP CRC32].mkv`, in order to improve alphabetical sort ordering. The original goal has expanded into a large number of transforms with a comprehensive test suite.
 
-Written in PHP, bash, batch
+## Usage
 
-Tags: anime
-
-=USAGE (v3)=
-
-`Usage:
+```
+Usage:
   shunt_tags [OPTIONS]
   
 Options:
@@ -23,9 +22,9 @@ Options:
   -r  --recursive               Apply to subdirectories. (false)
       --test-suite              Run test suite and exit  
       --undo                    Display an undo script
-`
+```
 
-=CHANGELOG=
+## Changelog
 
 2017-10-22 v3.0
 - Rewritten in PHP