4.2.3

@jpivarski fixed the use of Unicode names for objects in ROOT files: PR #577. Made flow=True mean the same thing for Uproot histograms as hist: PR #582. Added an interpretation for ROOT::VecOps::RVec: PR #593. Replaced an error message in HTTPSource with a fallback to the non-multipart-GET case: PR #594. Put an upper limit on the time KeyInFileError takes to print itself: PR #595.