YAML output uses objects for column definitions
YAML output uses objects for column definitions

For CREATE TABLE statements, change the output of YAML format for the
collection of column definitions to be a dict/object notation instead of
a list notation.

In other words, instead of this:

```
sqltoaster --yaml "CREATE TABLE t1 (a INT NOT NULL, b VARCHAR(200))"
statements:
- type: CREATE_TABLE
  table_name: t1
  column_definitions:
    - a INT NOT NULL
    - b VARCHAR(200)
(took 29636 nanoseconds)
```

we should get this:

```
sqltoaster --yaml "CREATE TABLE t1 (a INT NOT NULL, b VARCHAR(200))"
statements:
- type: CREATE_TABLE
  table_name: t1
  column_definitions:
    a: INT NOT NULL
    b: VARCHAR(200)
(took 29636 nanoseconds)
```

Issue #104

jaypipes/sqltoast,jaypipes/sqltoast