v0.7.0

Merge with @davvid's repository.

Full changelog, courtesy of @davvid:

Features:

• Multi-line strings are now emitted using block scalars.
• Error messages now contain a byte offset to aid debugging. (#176)
• Yaml now has or and borrowed_or methods. (#179)
• Yaml::load_from_bytes() is now available. (#156)
• The parser and scanner now return Err() instead of calling panic.

Development:

• The documentation was updated to include a security note mentioning that yaml-rust is safe because it does not interpret types. (#195)
• Updated to quickcheck 1.0. (#188)
• hashlink is now used instead of linked_hash_map.