update Cargo.toml and start writing README

Cargo.toml

@@ -6,5 +6,7 @@ authors = ["Tom Panton <pantonshire@gmail.com>"]
 license = "MIT"
 repository = "https://github.com/pantonshire/treacle"
 description = "Event debouncer"
+readme = "README.md"
+keywords = ["debounce", "debouncer"]
 
 [dependencies]

README.md

@@ -0,0 +1,13 @@
+# `treacle`
+A generic event debouncer for Rust, for grouping events which occur close together in time into a
+single event.
+
+For example, you may have some
+[templates](https://www.arewewebyet.org/topics/templating/)
+which you want to reload whenever a template file changes. However, if many small changes are made
+to the template files in quick succession, it would be wasteful to reload the templates for every
+change; instead, a debouncer could be used to group the changes that occur at a similar time into
+a single change, so the templates are only reloaded once.
+
+## Usage
+