Add tests to check Session id attr can be modified

Some modules, most notably Dancer2::Session::Cookie, require this to work.

See also #460.

Signed-off-by: Pedro Melo <melo@simplicidade.org>
Document the fact the Session id attr can be modified

Signed-off-by: Pedro Melo <melo@simplicidade.org>
Tidy tests using project .perltidyrc

Signed-off-by: Pedro Melo <melo@simplicidade.org>
reflect change
Merge branch 'pr/qa_for_session_id_is_rw'
Fixing whitespace characters problems

This is the result of running `whiter lib script t tools xt`.
Script `whiter` is the part of Test::Whitespaces module.

Here are the rules that this script uses:

 * Each line ends with "\n" (including the last line)
 * For new lines "\n" is used (not "\r\n")
 * There are no ending spaces on the lines
 * 4 spaces are used instead of tabs
 * No empty lines in the end of file
Fixing t/template.t
Merge branch 'whitespace'
Added whitespace characters test
Merge branch 'test_whitespace'
reflect change
Fixing tests

See #473.
Merge branch 'bessarabov-fixing_tests'