Say how the validator checks universal limits

Indicate it's future work to allow parameterization of those
limits.

CHANGES

@@ -4,6 +4,12 @@ v2016.6-dev 2016-09-16
  - Published the C++ interface for assembling, disassembling, validation, and
    optimization.
  - Support SPV_KHR_shader_draw_parameters in assembler, disassembler, parser.
+ - Validator has increased coverage:
+   - Checks "Data rules" in Universal Validation Rules, section 2.16.1
+   - WIP: Universal Limits.
+     - The minimum mandated upper bounds are checked.
+     - TODO: Parameterize the validator to allow larger limits accepted by
+       a more than minimally capable implementation.
  - Fixes issues:
    #429: Validator: Allow OpTypeForwardPointer and OpTypeStruct to reference
      undefined IDs

README.md

@@ -56,6 +56,13 @@ See [`syntax.md`](syntax.md) for the assembly language syntax.
 ### Validator
 
 *Warning:* The validator is incomplete.
+Check the [CHANGES](CHANGES) file for reports on progress.
+
+*Note*: The validator checks some Universal Limits, from section 2.17 of the SPIR-V spec.
+The validator will fail on a module that exceeds those minimum upper bound limits.
+It is future work to parameterize the validator to allow larger
+limits accepted by a more than minimally capable SPIR-V consumer.
+
 
 ### Optimizer