Call setter on explicitly quoted strings.

Fixes #7.
Support map merging.

Fixes #1.
Add support for marshaling durations.
Fix typo
Merge pull request #9 from shawnps/v1

Fix comment typo.
Fix Setter handling on non-pointer fields.

Fixes #8.
Merge branch 'v1' of github.com:go-yaml/yaml into v1
Note in LICENSE.libyaml the specific files covered.
workaround: add index to maps #22
add StringIndex type and fix tests #22