[zh_CN] rename zh to zh_CN for Simplified Chinese, leaving zh_TW for Traditional Chinese (ref: http://sphinx-doc.org/config.html#confval-language)
[zh] fix sphinx build warning
Update index.srt

Added details about "Improve this Doc" button and completed the offline options description.
[pt] Update installation.rst

Removed some empty lines and missconfigured characters causing directories listing to break.
[zh_CN] change folder back to zh, but keep language as zh_CN
Merge pull request #1755 from andtxr/patch-3

[pt] [2.x] Update installation.rst
Merge pull request #1745 from blackpuppy/zh

[zh_CN] rename zh to zh_CN
[zh_CN] add installation (only basic part, according to #1713)
Merge branch 'master' into zh
[zh_CN] fix errors in /zh/installation.rst
[zh_CN] add cakephp-overview
Merge pull request #1756 from blackpuppy/zh

[zh_CN] add basic installation & cakephp-overview
[pt] [2.x] Update index.rst

Added details about "Improve this Doc" button.
Corrected the uppercase mistake in one of the links.
Completed the offline options description.
Merge pull request #1752 from andtxr/patch-1

[pt] [2.x] Update index.srt
ComboSession issue with writing

Follow up with my commit of a year ago, https://github.com/cakephp/docs/commit/23fc03c12c3eea8456e895c2696444e037cdcc56, we realize that there is another issue with the ComboSession. Take for example, if you have a cache server with two nodes, namely node#1 and node#2.

1. Write data to cache. Cache server chosen node#1 - write successful.
2. By definition, if cache writing is successful, then you write the data into database by calling `parent::write`. Since step#1 is successful, no data has been written into the cake_session database yet.
3. This time, app issues a read. Read trying to read data from cache server. Cache server chosen node#2 - read failure. When read fails, it fall back to database reading. Now database do not have such session, so session is lost - user logged out.

To tackle this, we should always write to both cache and database to synchronize database to the cache servers.
[en] correct original text
Merge branch 'master' into zh
[fr] follow #1719
[fr] fix typos
[fr] follow #1717

Update views.rst, deprecation of $title_for_layout