Add more docs to structopt definitions

This makes the generated documentation a tad more explanatory.

src/bin/git-add-coauthor.rs

@@ -2,6 +2,8 @@ use git_mob::{parse_coauthors_file, write_coauthors_file, Author};
 use structopt::StructOpt;
 
 #[derive(StructOpt, Debug)]
+#[structopt(name="git-add-coauthor")]
+/// Add a co-author to your git mob.
 struct Opt {
     /// Co-author initials
     initials: String,

src/bin/git-delete-coauthor.rs

@@ -2,6 +2,8 @@ use git_mob::{get_available_coauthors, write_coauthors_file};
 use structopt::StructOpt;
 
 #[derive(StructOpt, Debug)]
+#[structopt(name="git-delete-coauthor")]
+/// Delete a co-author from your .git-coauthors file
 struct Opt {
     /// Initials of the co-author to delete
     initials: String,

src/bin/git-edit-coauthor.rs

@@ -3,6 +3,8 @@ use std::process;
 use structopt::StructOpt;
 
 #[derive(StructOpt, Debug)]
+#[structopt(name="git-edit-coauthor")]
+/// Edit a co-author in your .git-coauthors template
 struct Opt {
     /// Co-author initials
     initials: String,

src/bin/git-mob.rs

@@ -7,6 +7,8 @@ use std::process;
 use structopt::StructOpt;
 
 #[derive(StructOpt, Debug)]
+#[structopt(name="git-mob")]
+/// Assemble a group of co-authors to help you on your coding quest
 struct Opt {
     /// Prints list of available co-authors
     #[structopt(short, long)]