[fix] can't parse 'false' boolean value

in former implementation, if you specify a boolean value as 'false'
in manifest, it always returned the default value. Thus if you don't
specify a default value, an error will possibly occur showing that
can't fill the template file. If you specify a default value, then
the specification in manifest won't take effect.
merge with upstream's latest master branch
Merge pull request #74 from bluesalt/parse_bool_value

[fix] can't parse 'false' boolean value