No anonymous parameters

Otherwise we get this and the appveyor build fails:

```
warning: anonymous parameters are deprecated and will be removed in the next edition.
  --> tests\tests.rs:68:18
   |
68 |     fn from_vecs(CsvVecs) -> Self;
   |                  ^^^^^^^ help: try naming the parameter or explicitly ignoring it: `_: CsvVecs`
   |
   = note: `#[warn(anonymous_parameters)]` on by default
   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2018!
   = note: for more information, see issue #41686 <rust-lang/rust#41686>
error: linking with `i686-w64-mingw32-gcc` failed: exit code: 1
```

tests/tests.rs

@@ -65,7 +65,7 @@ pub type CsvVecs = Vec<Vec<String>>;
 
 pub trait Csv {
     fn to_vecs(self) -> CsvVecs;
-    fn from_vecs(CsvVecs) -> Self;
+    fn from_vecs(vecs: CsvVecs) -> Self;
 }
 
 impl Csv for CsvVecs {