Fixed mangled sentence from book; edited for clarity (rust-lang#266)

Fixed mangled sentence from book; edited for clarity

Author: fmoko

exercises/enums/README.md

@@ -1,6 +1,8 @@
 ### Enums
 
-Rust allows you to define a type called `enums` which allow you to enumerate possible values. In combination with enums, we have the concept of `pattern matching` in Rust, which makes it easy to run different code for different values of an enumeration. Enums, while available in many languages, Rust's enums are most similar to `algebraic data types` in functional languages, such as F#, OCaml, and Haskell.
+Rust allows you to define types called "enums" which enumerate possible values. 
+Enums are a feature in many languages, but their capabilities differ in each language. Rust’s enums are most similar to algebraic data types in functional languages, such as F#, OCaml, and Haskell.
+Useful in combination with enums is Rust's "pattern matching" facility, which makes it easy to run different code for different values of an enumeration.  
 
 #### Book Sections