CodeIgniter support some basic web security by default!

I think its better to enable this basic security options by default.
It’s more likely that users who build a new website or application from
ground up, and use CodeIgniter can get used to this and eventually turn
this off. From a web security perspective, we can support a more secure
web, by default! Who agrees?
Style Guide

Logical Operators
Use of || is discouraged as its clarity on some output devices is low
(looking like the number 11 for instance). && is preferred over AND but
either are acceptable, and a space should always precede and follow !
change back to original
back to original
Merge pull request #2866 from darwinel/develop

Style guide