Fix some minor nits in the manual page

First of all, thanks a lot for writing and maintaining microsocks! What do you think about these three commits? Two of them are trivial fixes, the third one - start sentences on a new line - is something I personally learned from my time as a FreeBSD doc committer; the FreeBSD project has a policy that mdoc manual pages should be written like that, both as a hint to the formatting software and also as a convenience when rewriting sentences: there is no need to reflow a whole paragraph that contains five or six sentences if you want to add four words to one of them. Of course, it is your decision whether to accept these changes; let me know if you think that some of them are not needed, I can drop them from the branch. BTW, it is great to see people writing mdoc manual pages! Over the years I have wondered why this is not more widespread; it is *so* much easier than using the "traditional" man macro set... Thanks again, and keep up the great work!