Add blog post about type signatures

blog/_posts/2016-01-24-type-signatures.md

@@ -0,0 +1,25 @@
+---
+layout: post
+title:  Type Signatures
+date:   2016-01-24 16:00:00 +0100
+author: Oskar Wickström
+categories: compiler
+comments: true
+---
+
+In the spirit of making Oden code more understandable and to help the developer
+writing the code, support for type signatures has been added in [Oden
+0.2.1-RC1](#). They are optional but recommended to use.
+
+{% highlight clojure %}
+(: identity (int -> int))
+(def (incr n) (+ n 1))
+
+(: twice ((#a -> #a) -> (#a -> #a)))
+(def (twice f x) (f (f x)))
+
+(: two int)
+(def two (twice incr 0))
+{% endhighlight %}
+
+If you find any issues please [report them on GitHub](https://github.com/oden-lang/oden/issues).