problems.md in trackler-2.0.1.1

- old
+ new

@@ -56,9 +56,10 @@
 variable-length-quantity | Encodings, slices, bitwise, Result
 phone-number |  option, format, unwrap_or, iters, match
 wordy | Result, string parsing, operators (optional)
 tournament |  enum, sorting, hashmap, structs
 custom-set |  generic over type, vector, equality, struct
+alphametics | string parsing, combinations, math, external crates (optional)
 
 ## Rust Gets Strange
 
 Exercises that pay the cost of Rust's [strangeness budget](http://words.steveklabnik.com/the-language-strangeness-budget). Features that are very specific to Rust.
 