Don't use `.o` at the end of executable file names

[cwant]

A lot of the examples create executables with a .o at the end of the file names, e.g.,

chpl --fast hello.chpl -o hello.o

Having an executable file with an extension .o defies the typical convention of .o files (an object file: compiled but unlinked code, which can't be executed on its own).

I would recommend (and am willing to do the work) to change the examples, for example replacing the above example with:

chpl --fast hello.chpl -o hello

[razoumov]

Hi Chris. Good idea! There are actually quite a lot of things I would like to edit in this repository. For example, there are lots of inconsistencies between the task-parallel and domain-parallel parts. However, I am the only maintainer, and HPC Carpentry set up the repository in such a way that any pull request needs to be approved before merging. As you can see, I submitted a pull request in September, ironically listing maintainers, and I still can't merge it, as I am the only maintainer, and the request needs an approving review. If you agree, please join as a maintainer, so that we could really edit these lessons. Thanks!