Bumped version to v1.2.1, added CHANGELOG entry, updated README hardf…

…ork section

CHANGELOG.md

@@ -6,6 +6,13 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 (modification: no type change headlines) and this project adheres to
 [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [1.2.1] - 2019-06-03
+
+- Added `Istanbul` HF candidate [EIP-1108](https://eips.ethereum.org/EIPS/eip-1108)
+  (`DRAFT`) updated `alt_bn128` precompile gas costs (see `hardforks/istanbul.json`)
+
+[1.2.1]: https://github.com/ethereumjs/ethereumjs-common/compare/v1.2.0...v1.2.1
+
 ## [1.2.0] - 2019-05-27
 
 **DRAFT Istanbul Hardfork Support**

README.md

@@ -62,6 +62,8 @@ to ease `blockNumber` based access to parameters.
 
 # Hardfork Params
 
+## Active Hardforks
+
 There are currently parameter changes by the following past and future hardfork by the
 library supported:
 
@@ -73,7 +75,19 @@ library supported:
 - `byzantium`
 - `constantinople`
 - `petersburg` (aka `constantinopleFix`, apply together with `constantinople`)
-- `istanbul` (`DRAFT`)
+
+## Future Hardforks
+
+Scope and technical details on the `Istanbul` HF are currently forming out
+within [EIP-1679](https://eips.ethereum.org/EIPS/eip-1679) respectively the
+associated EIP pages.
+
+Supported EIPs in the library:
+
+- [EIP-1108](https://eips.ethereum.org/EIPS/eip-1108) `alt_bn128` precompile
+  gas cost reductions (HF candidate, `DRAFT` status)
+
+## Parameter Access
 
 For hardfork-specific parameter access with the `param()` and `paramByBlock()` functions
 you can use the following `topics`:

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ethereumjs-common",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "description": "Resources common to all Ethereum implementations",
   "main": "./dist/index.js",
   "types": "./dist/index.d.ts",