Dumper should take into account booleans syntax from YAML 1.0/1.1

Related to issue #85
Improve loader/construct-bool functional test.
Add some comments.
Remove "bad idea" TODO remarks from the code.

Flow readers must not consume trailing whitespace because such a
behavior is too error-prone. Even plain scalar reader does not
consume that outside of it's scope (indentation level).

Example of wrong of "every reader consumes trailing whitespaces"
behavior is issue #80
Fix bug in flow collections reader.

Related to issue #92
Update HISTORY