Added a `migrate` alias.

It migrates the DB and prepares the test DB.

plugins/rails/rails.plugin.zsh

@@ -6,6 +6,7 @@ alias sr='ruby script/runner'
 alias ssp='ruby script/spec'
 alias rdbm='rake db:migrate'
 alias rdbtp='rake db:test:prepare'
+alias migrate='rake db:migrate && rake db:test:prepare'
 alias sc='ruby script/console'
 alias sd='ruby script/server --debugger'
 alias devlog='tail -f log/development.log'