add sdkch to maintain PENDING.md effectively and free of file conflicts

Closes: #2380

.pending/bugfixes/sdk/3837-Fix-WithdrawValidatorCommission-to-properly-set-the-validator-s-remaining-commission

@@ -0,0 +1 @@
+#3837 Fix `WithdrawValidatorCommission` to properly set the validator's remaining commission.

.pending/features/sdk/3813-New-sdk-NewCoins-safe-constructor-to-replace-bare

@@ -0,0 +1 @@
+#3813 New sdk.NewCoins safe constructor to replace bare sdk.Coins{} declarations.

.pending/improvements/gaia/3808-gaiad-and-gaiacli-integration-tests-use-build-binaries

@@ -0,0 +1 @@
+#3808 `gaiad` and `gaiacli` integration tests use ./build/ binaries.

.pending/improvements/gaiacli/3859-Add-newline-to-echo-of-gaiacli-keys

@@ -0,0 +1 @@
+#3859 Add newline to echo of `gaiacli keys ...`

.pending/improvements/sdk/3801-baseapp-safety-improvements

@@ -0,0 +1 @@
+#3801 `baseapp` safety improvements

.pending/improvements/sdk/3820-Make-Coins-IsAllGT-more-robust-and-consistent

@@ -0,0 +1 @@
+#3820 Make Coins.IsAllGT() more robust and consistent.

.pending/improvements/sdk/3828-New-sdkch-tool-to-maintain-changelogs

@@ -0,0 +1 @@
+#3828 New sdkch tool to maintain changelogs

Makefile

@@ -123,6 +123,7 @@ devtools-stamp: tools
 	@echo "--> Downloading linters (this may take awhile)"
 	$(GOPATH)/src/github.com/alecthomas/gometalinter/scripts/install.sh -b $(GOBIN)
 	go get github.com/tendermint/lint/golint
+	go install ./cmd/sdkch
 	touch $@
 
 vendor-deps: tools

cmd/sdkch/README.md

@@ -0,0 +1,51 @@
+# sdkch
+Simple tool to maintain modular changelogs
+
+# Usage
+
+```
+$ sdkch -help
+usage: sdkch COMMAND
+
+Maintain unreleased changelog entries in a modular fashion.
+
+Commands:
+    init
+    add SECTION STANZA            Add an entry file.
+                                  Read from stdin until it
+                                  encounters EOF.
+    generate [VERSION]            Generate a changelog in
+                                  Markdown format and print it
+                                  to stdout. VERSION defaults
+                                  to UNRELEASED.
+
+    Sections             Stanzas
+         ---                 ---
+    breaking                gaia
+    features             gaiacli
+improvements            gaiarest
+    bugfixes                 sdk
+                      tendermint
+
+Flags:
+  -d string
+    	entry files directory (default "./.pending")
+```
+
+## Add a new entry
+
+You can either drop a text file in the appropriate directory or use the `add` command:
+
+```bash
+$ sdkch add features gaiacli '#3452 New cool gaiacli command'
+```
+
+If no message is provided, a new entry file is opened in an editor is started
+
+## Generate the full changelog
+
+```bash
+$ sdkch generate
+```
+
+The `-prune` flag would remove the old entry files after the changelog is generated.