docs(select): clarify usage

The wording seemed confusing and these adjustments seem to capture the intent
with less turbulence.

Closes #4257
docs(tutorial): update examples to show best practices

Closes #4256, #4255, #4254, #4253, #4250, #4092
docs(tutorial): improve wording and consistency
Merge branch 'master' of https://github.com/angular/angular.js
componentizd!