doc: Response.replace() cannot take meta argument

>>> response.replace(meta={'foo':1})
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/srv/scrapy/scrapy-fork/scrapy/scrapy/http/response/text.py", line 45, in replace
    return Response.replace(self, *args, **kwargs)
  File "/srv/scrapy/scrapy-fork/scrapy/scrapy/http/response/__init__.py", line 77, in replace
    return cls(*args, **kwargs)
  File "/srv/scrapy/scrapy-fork/scrapy/scrapy/http/response/text.py", line 22, in __init__
    super(TextResponse, self).__init__(*args, **kwargs)
TypeError: __init__() got an unexpected keyword argument 'meta'
doc: remove trailing spaces
Merge pull request #275 from stav/doc

doc: Response.replace() cannot take meta argument