docs: small improvements (#2933)

* update docs

- make install_c cmd (install)
- explain node IDs (quick-start)
- update UPGRADING section (using-tendermint)

* use git clone with JS example

JS devs may not have Go installed and we should not force them to.

* rewrite sentence

docs/app-dev/getting-started.md

@@ -252,12 +252,11 @@ we'll run a Javascript version of the `counter`. To run it, you'll need
 to [install node](https://nodejs.org/en/download/).
 
 You'll also need to fetch the relevant repository, from
-[here](https://github.com/tendermint/js-abci) then install it. As go
-devs, we keep all our code under the `$GOPATH`, so run:
+[here](https://github.com/tendermint/js-abci), then install it:
 
 ```
-go get github.com/tendermint/js-abci &> /dev/null
-cd $GOPATH/src/github.com/tendermint/js-abci/example
+git clone https://github.com/tendermint/js-abci.git
+cd js-abci/example
 npm install
 cd ..
 ```
@@ -276,13 +275,16 @@ tendermint node
 ```
 
 Once again, you should see blocks streaming by - but now, our
-application is written in javascript! Try sending some transactions, and
+application is written in Javascript! Try sending some transactions, and
 like before - the results should be the same:
 
 ```
-curl localhost:26657/broadcast_tx_commit?tx=0x00 # ok
-curl localhost:26657/broadcast_tx_commit?tx=0x05 # invalid nonce
-curl localhost:26657/broadcast_tx_commit?tx=0x01 # ok
+# ok
+curl localhost:26657/broadcast_tx_commit?tx=0x00
+# invalid nonce
+curl localhost:26657/broadcast_tx_commit?tx=0x05
+# ok
+curl localhost:26657/broadcast_tx_commit?tx=0x01
 ```
 
 Neat, eh?