Update index.srt

Added details about "Improve this Doc" button and completed the offline options description.
[zh_CN] done /zh_CN/cakephp-overview/where-to-get-help.rst
[zh_CN] fix errors in /zh/installation.rst
[zh_CN] done /zh/cakephp-overview/what-is-cakephp-why-use-it.rst
[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
[en] correct original text
[zh_CN] improve translation
[zh_CN] use Unix line endings instead of Windows ones
[zh_CN] done /zh/tutorials-and-examples/blog/blog.rst
[en] correct original text
Merge branch 'master' into zh
Merge branch 'zh' into zh-work

Conflicts:
	zh/cakephp-overview/what-is-cakephp-why-use-it.rst
	zh/contents.rst
	zh/epub-contents.rst
	zh/pdf-contents.rst