Convert CLI to urfave v2

Followed the Migration Guide at https://cli.urfave.org/migrate-v1-to-v2/
The major changes not pointed out in the migration guide are:
- context.Args() no longer produces a []slice, so context.Args().Slice()
  in substitued
- All cli.Global***** are deprecated (the migration guide is somewhat
  unclear on this)

Signed-off-by: Derek Nola <derek.nola@suse.com>

Vendor in urfave cli/v2

Signed-off-by: Derek Nola <derek.nola@suse.com>

Fix NewStringSlice calls

Signed-off-by: Derek Nola <derek.nola@suse.com>

vendor/github.com/xrash/smetrics/doc.go

@@ -0,0 +1,19 @@
+/*
+Package smetrics provides a bunch of algorithms for calculating
+the distance between strings.
+
+There are implementations for calculating the popular Levenshtein
+distance (aka Edit Distance or Wagner-Fischer), as well as the Jaro
+distance, the Jaro-Winkler distance, and more.
+
+For the Levenshtein distance, you can use the functions WagnerFischer()
+and Ukkonen(). Read the documentation on these functions.
+
+For the Jaro and Jaro-Winkler algorithms, check the functions
+Jaro() and JaroWinkler(). Read the documentation on these functions.
+
+For the Soundex algorithm, check the function Soundex().
+
+For the Hamming distance algorithm, check the function Hamming().
+*/
+package smetrics