tech(build): replace npm with yarn (#7108)

* tech(build): replace npm with yarn

* tech(build): change node version for CI

Makefile

@@ -4,7 +4,7 @@ deps-go:
 	go run build.go setup
 
 deps-js:
-	npm install
+	yarn install
 
 deps: deps-go deps-js
 

README.md

@@ -114,7 +114,8 @@ To build less to css for the frontend you will need a recent version of **node (
 npm (v2.5.0) and grunt (v0.4.5). Run the following:
 
 ```bash
-npm install
+npm install -g yarn
+yarn install
 npm run build
 ```
 

appveyor.yml

@@ -11,7 +11,8 @@ environment:
 install:
   # install nodejs and npm
   - ps: Install-Product node $env:nodejs_version
-  - npm install
+  - npm install -g yarn
+  - yarn install
   - npm install -g grunt-cli
   # install gcc (needed for sqlite3)
   - choco install -y --limit-output mingw

circle.yml

 machine:
   node:
-    version: 5.11.1
+    version: 6.9.2
   environment:
     GOPATH: "/home/ubuntu/.go_workspace"
     ORG_PATH: "github.com/grafana"

docs/sources/project/building_from_source.md

@@ -40,7 +40,8 @@ To build less to css for the frontend you will need a recent version of node (v0
 npm (v2.5.0) and grunt (v0.4.5). Run the following:
 
 ```
-npm install
+npm install -g yarn
+yarn install
 npm install -g grunt-cli
 grunt
 ```

scripts/circle-test.sh

@@ -13,8 +13,8 @@ function exit_if_fail {
 cd /home/ubuntu/.go_workspace/src/github.com/grafana/grafana
 
 rm -rf node_modules
-npm install -g npm
-npm install
+npm install -g yarn
+yarn install
 
 exit_if_fail npm test
 exit_if_fail npm run coveralls