Many of the examples provided within documentation are using a single
dash for the command line arguments, but the telegraf executable
explicitly has two dashes.
There are also some inconsistencies with the ordering of the command
line argument examples. I've ordered them so that the examples will
show: config, config-directory, input-filter, test
this is so that we don't call os.Stat twice for every file matched
by Match(). Also changing the behavior to _not_ return the name of a
file that doesn't exist if it's not a glob.
