🐛 Fixed option collision with commander (--version vs --v)

no issue

- `--version` is a reserved option (see tj/commander.js#648). Same applies to `--name` etc.
- We have to use `--v` for now.
- This is in theory a breaking change, but the feature never worked when using `knex-migrator rollback --version x.x.x` in the shell
  - that's why it's a bug fix
- updated docs

README.md

@@ -102,6 +102,8 @@ knex-migrator reset [resets your database]
 knex-migrator reset --force [resets your database and ignores the migration lock]
 
 knex-migrator rollback
+knex-migrator rollback --force
+knex-migrator rollback --force --v 1.20.0
 ```
 
 ### JS

bin/knex-migrator-rollback

@@ -1,17 +1,17 @@
 #!/usr/bin/env node
 
-let program = require('commander');
-let utils = require('../lib/utils');
+const program = require('commander');
+const utils = require('../lib/utils');
 
-let logging = require('../logging');
+const logging = require('../logging');
 let knexMigrator;
 
 utils.getKnexMigrator({path: process.cwd()})
     .then(function (KnexMigrator) {
         program
             .option('--mgpath <path>')
             .option('--force')
-            .option('--version')
+            .option('--v <version>', 'The version to rollback to.')
             .parse(process.argv);
 
         try {
@@ -21,7 +21,7 @@ utils.getKnexMigrator({path: process.cwd()})
             process.exit(1);
         }
 
-        return knexMigrator.rollback({force: program.force, version: program.version})
+        return knexMigrator.rollback({force: program.force, version: program.v})
             .then(function () {
                 logging.info('Rollback was successful.');
             });

lib/index.js

@@ -1130,7 +1130,7 @@ KnexMigrator.prototype.isDatabaseOK = function isDatabaseOK() {
  * You can pass `--force` to skip this.
  *
  * `knex-migrator rollback --force` does only rollback the current version you are on.
- * `knex-migrator rollback --force --version 1.20` does rollback all migration scripts between the version you are on
+ * `knex-migrator rollback --force --v 1.20` does rollback all migration scripts between the version you are on
  *  and to the version you have specified (but this version is excluded).
  *
  *  "Rollback to version 1.22" => That means i want to bring back my blog to 1.22. Rollback 1.23, 1.24 etc.