tech(build): yarn install should use --pure-lockfile

Makefile

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

README.md

@@ -115,7 +115,7 @@ npm (v2.5.0) and grunt (v0.4.5). Run the following:
 
 ```bash
 npm install -g yarn
-yarn install
+yarn install --pure-lockfile
 npm run build
 ```
 

appveyor.yml

@@ -12,7 +12,7 @@ install:
   # install nodejs and npm
   - ps: Install-Product node $env:nodejs_version
   - npm install -g yarn
-  - yarn install
+  - yarn install --pure-lockfile
   - npm install -g grunt-cli
   # install gcc (needed for sqlite3)
   - choco install -y --limit-output mingw

docs/sources/project/building_from_source.md

@@ -41,7 +41,7 @@ npm (v2.5.0) and grunt (v0.4.5). Run the following:
 
 ```
 npm install -g yarn
-yarn install
+yarn install --pure-lockfile
 npm install -g grunt-cli
 grunt
 ```

scripts/circle-test.sh

@@ -14,7 +14,7 @@ cd /home/ubuntu/.go_workspace/src/github.com/grafana/grafana
 
 rm -rf node_modules
 npm install -g yarn
-yarn install
+yarn install --pure-lockfile
 
 exit_if_fail npm test
 exit_if_fail npm run coveralls