Implement user "bio" field

Perhaps this should be an extension, but it is pretty essential and I
can’t think of many instances where it wouldn’t be wanted. Would be
very easy to extract later on if need be.

framework/core/migrations/2015_02_24_000000_create_users_table.php

@@ -21,6 +21,8 @@ class CreateUsersTable extends Migration {
             $table->string('confirmation_token')->nullable();
             $table->boolean('is_activated')->default(0);
             $table->string('password');
+            $table->text('bio')->nullable();
+            $table->text('bio_html')->nullable();
             $table->dateTime('join_time')->nullable();
             $table->dateTime('last_seen_time')->nullable();
             $table->dateTime('read_time')->nullable();