Added documentation for context, param_parser and route

src/kemal/context.cr

@@ -1,3 +1,5 @@
+# Context is the environment which holds request/response specific
+# information such as params, content_type e.g
 class Kemal::Context
   getter request
   getter params

src/kemal/param_parser.cr

@@ -1,3 +1,6 @@
+# ParamParser parses the request contents including query_params and body
+# and converts them into a params hash which you can within the environment
+# context.
 class Kemal::ParamParser
   def initialize(@route, @request)
     @route_components = route.components

src/kemal/route.cr

@@ -1,3 +1,6 @@
+# Route is the main building block of Kemal.
+# It takes 3 parameters method, path and a block to specify
+# what action to be done if the route is matched.
 class Kemal::Route
   getter handler
   getter components