Merge pull request #186 from dkotrada/patch-2

More clear table headers

Author: ehuss

src/rust-2018/cargo-and-crates-io/cargo-check-for-faster-checking.md

@@ -47,8 +47,8 @@ So how much speedup do you actually get? Like most performance related
 questions, the answer is "it depends." Here are some very un-scientific
 benchmarks at the time of writing.
 
-|  build | performance | check performance | speedup |
+|  use case | build performance | check performance | speedup |
 |--------|-------------|-------------------|---------|
 | initial compile | 11s | 5.6s | 1.96x |
 | second compile (no changes) | 3s | 1.9s | 1.57x |
-| third compile with small change | 5.8s | 3s | 1.93x |
+| third compile with small change | 5.8s | 3s | 1.93x |