* added encoding aliases, configurable through a new ENCODING_ALIASES setting
* Response.encoding now returns the real encoding detected for the body
* simplified TextResponse API by removing body_encoding() and
headers_encoding() methods
* Response.encoding now tries to infer the encoding from the body always (it
was done before only on HtmlResponse and TextResponse)
* removed scrapy.utils.encoding.add_encoding_alias() function
* updated implementation of scrapy.utils.response function to reflect these API
changes
* updated documentation to reflect API changes
