Bug fixes

• Fix argument consistency between S3 generics and methods.

• as_blob(NA_character_) returns a missing blob instead of as_blob("NA") (#26, @MichaelChirico).

• Moved to "stable" lifecycle stage.
• Remove is_vector_s3() (#19).

• Inline prettyunits.
• vec_ptype2.hms.default() forwards to vec_default_ptype2() for compatibility with vctrs 0.2.1.

Breaking changes

• The blob class is now based on list_of(raw()) from the vctrs package (#11). This adds support for vec_cast() and vec_ptype2(). Some operations (such as subset assignment) are now stricter. The new_blob() constructor permits safe and fast construction of blob objects from a list, and validate_blob() checks an existing object for conformity with the rules.

• The new is_blob() deprecates the existing is.blob(). as.blob() is deprecated in favor of vec_cast() or the new as_blob() (which is just a thin wrapper around vec_cast()).

• Indexing a vector of blobs out of bounds now raises an error. Use NA as index to create a NULL blob.

• Now suggesting pillar instead of importing tibble, and using colored
  formatting with the prettyunits package with B instead of b as units
  (#7, #9).

• The blob class can now be used for S4 dispatch.

• Calling c() on blob objects returns a blob.

• New maintainer: Kirill Müller.
• Added as.blob.blob()and as.data.frame.blob() methods (#3).
• Size of very large blobs is displayed correctly.