FAQ: add required extension

Github-fix: denisenkom#265
Signed-off-by: Nicolas Sebrecht <nicolas.sebrecht@1001pneus.fr>

FAQ.md

@@ -16,39 +16,39 @@
   NilMigration defines a migration without a body. NilVersion is defined as const -1.
 
 #### What is the difference between uint(version) and int(targetVersion)?
-  version refers to an existing migration version coming from a source and therefor can never be negative. 
-  targetVersion can either be a version OR represent a NilVersion, which equals -1.    
+  version refers to an existing migration version coming from a source and therefor can never be negative.
+  targetVersion can either be a version OR represent a NilVersion, which equals -1.
 
 #### What's the difference between Next/Previous and Up/Down?
   ```
-  1_first_migration.up           next ->  2_second_migration.up      ...
-  1_first_migration.down  <- previous     2_second_migration.down    ...
+  1_first_migration.up.extension           next ->  2_second_migration.up.extension      ...
+  1_first_migration.down.extension  <- previous     2_second_migration.down.extension    ...
   ```
- 
+
 #### Why two separate files (up and down) for a migration?
-  It makes all of our lives easier. No new markup/syntax to learn for users 
+  It makes all of our lives easier. No new markup/syntax to learn for users
   and existing database utility tools continue to work as expected.
-    
+
 #### How many migrations can migrate handle?
-  Whatever the maximum positive signed integer value is for your platform. 
-  For 32bit it would be 2,147,483,647 migrations. Migrate only keeps references to 
-  the currently run and pre-fetched migrations in memory. Please note that some 
+  Whatever the maximum positive signed integer value is for your platform.
+  For 32bit it would be 2,147,483,647 migrations. Migrate only keeps references to
+  the currently run and pre-fetched migrations in memory. Please note that some
   source drivers need to do build a full "directory" tree first, which puts some
-  heat on the memory consumption. 
-    
+  heat on the memory consumption.
+
 #### Are the table tests in migrate_test.go bloated?
   Yes and no. There are duplicate test cases for sure but they don't hurt here. In fact
   the tests are very visual now and might help new users understand expected behaviors quickly.
-  Migrate from version x to y and y is the last migration? Just check out the test for 
+  Migrate from version x to y and y is the last migration? Just check out the test for
   that particular case and know what's going on instantly.
-    
+
 #### What is Docker being used for?
   Only for testing. See [testing/docker.go](testing/docker.go)
-    
+
 #### Why not just use docker-compose?
   It doesn't give us enough runtime control for testing. We want to be able to bring up containers fast
   and whenever we want, not just once at the beginning of all tests.
-    
+
 #### Can I maintain my driver in my own repository?
   Yes, technically thats possible. We want to encourage you to contribute your driver to this respository though.
   The driver's functionality is dictated by migrate's interfaces. That means there should really
@@ -64,4 +64,4 @@
   which prevents attempts to run more migrations on top of a failed migration. You need to manually fix the error
   and then "force" the expected version.
 
-  
+