Mention related packages in README

[goretkin]

https://github.com/archermarx/PartialFunctions.jl

@archermarx , @MrBreadWater I wonder if you think it is worthwhile to combine the functionality of these two packages.

[archermarx]

Yeah it's worth considering! I need to look more at this package but I took a lot of my implementation details from how base implemented Fix1 and so on. Would be very useful

[goretkin]

https://github.com/Tokazama/ChainedFixes.jl/blob/master/src/ChainedFixes.jl#L213-L247

[MrBreadWater]

Ooh, this would be a nice pairing. Though, I probably couldn't be of much help, because my 'contribution' to PartialFunctions consisted of 1 line a couple days ago.

[goretkin]

https://github.com/MasonProtter/LegibleLambdas.jl
https://github.com/c42f/Underscores.jl
https://github.com/tkf/UnderscoreOh.jl

[MrBreadWater]

Could be useful to combine even more of these packages, like the ones you linked, into one for a larger module. I've seen a lot of smaller modules (ie PartialFunctions, this one) aimed towards a common goal of implementing more "Functional" aspects to Julia or making it easier to use what's already in place, and all are fairly good on their own, but they might be able to work together far better if they merged.