fix .status= case sensitivity

docs/api.md

@@ -129,7 +129,7 @@ app.context({
 
 ### ctx.status=
 
-  Set response status via numeric code or string:
+  Set response status via numeric code or case-insensitive string:
 
   - 100 "continue"
   - 101 "switching protocols"

lib/context.js

@@ -66,7 +66,7 @@ module.exports = {
 
   set status(val) {
     if ('string' == typeof val) {
-      var n = statuses[val];
+      var n = statuses[val.toLowerCase()];
       if (!n) throw new Error(statusError(val));
       val = n;
     }

test/context.js

@@ -156,6 +156,12 @@ describe('ctx.status=', function(){
         ctx.status = 'forbidden';
         ctx.status.should.equal(403);
       })
+
+      it('should be case-insensitive', function(){
+        var ctx = context();
+        ctx.status = 'ForBidden';
+        ctx.status.should.equal(403);
+      })
     })
 
     describe('and invalid', function(){