Fixed problem when the response is "Not Found"

When the response from TMDB is "Not Found" an exception was raised when
gsub was called on etag since etag was nil.
Fixed encoding problem with symbol ‘

The symbol ‘ was causing an error when the specs had to run, with this
magic comment is fixed now.
Added simple people spec
Merge pull request #19 from josem/master

Fixed encoding problem, added simple people spec and checked when the etag param is nil