Typo in Put.java class documentation

There is a typo in the class documentation of Put.java, which got introduced in commit 21ddb60.

The documentation says "To perform a Put, instantiate a Put object with the row to insert to and for eachumn to be inserted..."

It should say "... for each column ..."

I know there are more important issues than this one. I had already forked and submitted a PR, but it seems that I was not following the proper procedure for bug reporting and fixing.