#1210: Add rule 'rails_migrations_pending'

* Add rule 'rails_migrations_pending'

* Update thefuck/rules/rails_migrations_pending.py

Co-authored-by: Pablo Aguiar <scorphus@gmail.com>

* Add initial command to corrected command

Co-authored-by: Pablo Aguiar <scorphus@gmail.com>

README.md

@@ -310,6 +310,7 @@ following rules are enabled by default:
 * `python_module_error` – fixes ModuleNotFoundError by trying to `pip install` that module;
 * `quotation_marks` – fixes uneven usage of `'` and `"` when containing args';
 * `path_from_history` – replaces not found path with a similar absolute path from history;
+* `rails_migrations_pending` – runs pending migrations;
 * `react_native_command_unrecognized` – fixes unrecognized `react-native` commands;
 * `remove_shell_prompt_literal` – remove leading shell prompt symbol `$`, common when copying commands from documentations;
 * `remove_trailing_cedilla` – remove trailing cedillas `ç`, a common typo for European keyboard layouts;