Curly-decimals string format.
E.g. cdfmt("Hi, {0}! Pls, {1} the {2}.")("Smith", "frobnicate", "quibplatz") => "Hi, Smith! Pls, frobnicate the quibplatz!".
cdfmt("Hi, {0}! Pls, {1} the {2}.")("Smith", "frobnicate", "quibplatz")
"Hi, Smith! Pls, frobnicate the quibplatz!"
Credits: https://gist.github.com/0i0/1519811