i18n guide: remove link to external page about 'How to encode the current locale in the URL' as it no longer exists

i18n guide: it's activerecord.errors.messages.record_invalid (instead of 'invalid'), and messagges typo

remove old school validations and replaced with new validates method. Pending: fix active_record guide

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

class inheritable attributes is used no more! all internal use of class inheritable has been changed to class_attribute. class inheritable attributes has been deprecated.
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

* Examples running with the text are preferred over separate Example
  sections.
* No need to call puts, in # => we show the return value, not STDOUT.
* Say explicitly that double quotes are removed.
* Specify that we are talking \uXXX, rather than, say, HTML entities.

instantiate the delegate object after initialize is defined so that our initialize method actually gets called

Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

According to http://www.ietf.org/rfc/rfc2616.txt and
http://tools.ietf.org/rfc/rfc3986.txt [ and ] are reserved characters
and should be escaped using "%" HEX HEX

This reverts commit 856d2fd8 and
1ee9b40b..