Formatting.jl is broken on v0.6

[ScottPJones]

It looks like this is caused by JuliaLang/julia#17057.
The relevant code is in cformat.jl (the generate_formatter function), where it creates a function that wraps a call to @sprintf with quote, and then uses eval and stores the function into a Dict to memoize it based on the format string.
This worked previous to 17057 on master, but now it gets the following error:

ERROR: LoadError: LoadError: MethodError: no method matching (::##1#2)(::Float64)
The applicable method may be too new: running in world age 21340, while current world is 21341.
Closest candidates are:
  #1(::Any) at /j/Formatting.jl/test/cformat.jl:10 (method too new to be called from this world context.)
Stacktrace:
 [1] test_equality() at /j/Formatting.jl/test/cformat.jl:15

[ScottPJones]

Fixed by #29