Add example in xyz2grd

[anbj]

Add man page example in xyz2grd.rst. I see that my old commit also is included in this PR.

[PaulWessel]

Could you remove your old commit from this one since those changes are already in master?

[anbj]

Will try - not fluent in github yet.

[PaulWessel]

Likewise...

[seisman]

@abanbj You need to rebase your add-example-in-xyz2grd with gmt's master branch.

Assuming that you have a local copy and have added the gmt official repo as a remote repo and named it as upstream. You can follow these steps to rebase your branch:

git fetch upstream master   # fetch the latest master branch from upstream
git checkout add-example-in-xyz2grd  # switch to your branch
git rebase upstream/master   # rebase your branch with gmt's master branch
# push your local branch to your github repo
# you need -f option to force pushing, since rebasing changed the commit history of the branch
git push -f                   

[anbj]

Thank you for helping me out @seisman. Made a new PR!