test: add sample with 10k unique keys

Input created via
```sh
bash -c 'for i in {1..10000} ; do echo "id$i;0.0" ; done' >./src/test/resources/samples/measurements-10000-unique-keys.txt
```
and output via baseline implementation.

Keys are short and very similar which improves chances for collision
and hence are good for testing.

Fixes #91

.gitignore

@@ -43,5 +43,5 @@ out/
 
 # 1BRC
 /measurements*.txt
-*.out
+/*.out
 out_expected.txt