Atomic S3 classes with format methods now use those methods when
displaying comparisons (#98). If the printed representation is the
same, they fallback to displaying the underlying data.

Rowwise data frame comparisons are now much much faster (#116),
and respect the max_diffs argument (@krlmlr, #110).

Unnamed environments now compare by value, not by reference (i.e. if
two environments contain the same values, they compare the same, even
if they're different environments) (#127). Environments that contain
self-references are handled correctly (#117). Differences between pairs
of environments are only ever reported once.

In the unlikely event that you have bare CHARSXP objects, waldo now
handles them (#121).

S4 objects are labelled with their class, not all superclasses (#125).

compare_proxy() ignores the "index" attribute for data tables
(@krlmlr, #107), and works again for RProtoBuf objects
(@MichaelChirico, #119)

Infinite values can be compared with a tolerance (@dmurdoch, #122).