v2.9.0

Measurements v2.9.0

Diff since v2.8.0

Closed issues:

• Can't use unique with measurements (#124)
• Measurements.value(x::Missing) = missing (#126)
• one(measurement) should return 1, not 1 ± 0 (#134)

Merged pull requests:

• add value(::Missing) & uncertainty(::Missing) (#127) (@Eben60)
• Add docstrings for value(::Missing) & uncertainty(::Missing) (#128) (@Eben60)
• Define one(::Type{Measurement{T}}) to return one(T) (#135) (@giordano)
• Use more @inferred in tests (#136) (@giordano)