added wc utility

Hello!

I wrote a little "wc" in rust - it seems to work well with most files, although files generated from /dev/random give the counts a bit of trouble but I don't know how much of an issue that is.

eg

```
~/rusty/coreutils/wc$ head -c 1000000 /dev/urandom > random.txt # 10 MB
~/rusty/coreutils/wc$ ./wc random.txt 
   39082   233777 10000000 random.txt
~/rusty/coreutils/wc$ wc random.txt 
   39081   220865 10000000 random.txt
```