v0.12.0

[maciejhirsz]

• Updated to edition 2018.
• Simplified reading escaped unicode in strings a bit.
• Provided From<&[T]> implementation for JsonValue where T: Into<JsonValue> (closes cannot borrow variables in object! #160).
• object! and array! macros will no longer re-allocate (closes object! performance could be improved #159).
• BREAKING HashMap and BTreeMap conversions are now more generic, working for any pair of K key and V value where K: AsRef<str> and V: Into<JsonValue>. This means that type inference won't always work in your favor, but should be much more flexible.
• You can now .collect() an interator of (K, V) (with bounds same as point above) into an Object.