doc: update v0.7.0 changelog

Signed-off-by: David Aguilar <davvid@gmail.com>
jsonpickle: add a "safe-mode" when decoding objects

Avoid usage of eval() when in safe mode.  We may later break backwards
compatibility and switch the default value of "safe" from False to True,
but for now we are simply making the new mode available.

Signed-off-by: David Aguilar <davvid@gmail.com>
jsonpickle v0.7.0

Signed-off-by: David Aguilar <davvid@gmail.com>