GCC Compatibillity

[Manicqin]

Hi I've made some changes to help the cross compatibility.
I have also entered some changes following some warnings of my IDE (removing void from no argument functions and adding explicit to single parameter functions).

I only changed the "wordcount" example for now.

this code was tested on VS14 and GCC 7.2.0

[jainvasu631]

This branch is not compiling due to One error and One warning.
Error
In file included from include/detail/intermediates.hpp:6:0, from include/mapreduce.hpp:137, from PageRank.cpp:12: include/detail/intermediates/local_disk.hpp:7:19: fatal error: job.hpp: No such file or directory #include "job.hpp"
Should be #include "../job.hpp"
Warning
include/detail/platform.hpp: In function ‘std::__cxx11::string mapreduce::linux_os::get_temporary_filename(std::__cxx11::string&)’: include/detail/platform.hpp:85:12: warning: ignoring return value of ‘int mkstemp(char*)’, declared with attribute warn_unused_result [-Wunused-result]

The line needs to be replaced by auto tmp2 = mkstemp(tmpfile);

I have fixed these errors and warning and created a new Pull Request