Update README and add support for configuration file

.configuration.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+export $PSQL_OPTS=
+export $DB_NAME=

README.md

@@ -2,12 +2,53 @@
 
 [Startup Engineering - Roll your own Database Migrations](http://ian-shafer.github.io/2016/02/02/db-migrations/)
 
-### Required table
+## Setup
+
+#### Configuration
+All configuration needed is done in .configuration.sh.
+Note that a
+[.pgpass](http://www.postgresql.org/docs/9.3/static/libpq-pgpass.html) file will
+do most of the times as well and therefore configuration is not mandatory.
+
+#### Migration files
+The files in the /migrations directory are changes to the scheme, not the full
+scheme.
+
+The naming convention for migration files are:
+- 000.000
+- 000.001
+- 000.002
+- 000.003
+- 000.004
+- ...and so on
+
+**Example**
+The first file, `migration/000.000` may look like this:
+```
+create table users (
+  name varchar(32) not null,
+  primary key (name)
+);
+```
+
+The second file, `migration/000.001` may look like this:
+```
+alter table users
+add email varchar(256) not null;
+```
+
+#### Prerequisites
+One table needs to be created for the database to make this work:
 
 ```
-create table database_versions (
+CREATE TABLE database_versions (
   version varchar(32) not null,
   is_active boolean not null default false,
   creation_date timestamp not null default current_timestamp
 );
 ```
+
+To do the actual migration, then just run:
+```
+# ./db-upgrade
+```

db-upgrade

@@ -1,6 +1,6 @@
 #!/bin/bash
 set -e
-# source $(dirname $0)/../.include
+source .configuration.sh
 
 function add-version() {
   psql $PSQL_OPTS -c "update database_versions set is_active = false where is_active = true" $DB_NAME