word_pattern.cpp compiler error

After clone project, execute those commands
```
rm -rf CMakeCache.txt CMakeFiles
cmake .
make
```
meeting errors in word_pattern.cpp, says "_istream_iterator’ is not a member of ‘std’_", according to this [discussion](https://stackoverflow.com/questions/30694570/c-istream-iterator-is-not-a-member-of-std/30694579), considing adding 
> #include \<iterator\>
