explained why AR is used in an example for scenarios  doc
fixed extension documentation
Added Html::error().
Update apps-basic.md

update path document root
Update apps-advanced.md

document roots and composer folder params
Merge pull request #760 from lancecoder/patch-4

Update apps-advanced.md
Merge pull request #759 from lancecoder/patch-3

Update apps-basic.md
Update installation.md
Merge pull request #761 from lancecoder/patch-5

Update installation.md
Update caching.md
Merge pull request #762 from lancecoder/patch-6

Update caching.md
Fixes #763: handling empty string for date formatting.
Update main.php
Update main.php
Update main.php
Fixes #763.
Merge pull request #768 from lancecoder/patch-1

charset
Exit error handling to avoid handling exceptions multiple times.
refactored ActiveField.