Reflection: Fix broken SQL statement for text-typed default values.
You mean quotation marks, not parentheses... I think the better way to fix this would be to introspect the field type rather than the default value. You are right ... "quotation marks" it is. 

I decided to check the type of the default value because even if you have a certain numeric field type the default value could be any type depending on the users input. E.g. the following is certainly possible:

    import peewee as pw
    class A(pw.Model):
        name = pw.CharField(default=1)
        num = pw.IntegerField(default="foo")

I know it makes no sense but peewee allows to set defaults that don' t match the field type. Maybe that should get checked, too. But to prevent the SQL-statement from breaking it seams better to me to check the type of the default value.

When using the refection module on text-typed (unicode on py2, str on py3) Columns with default values there were parantheses missing around the generated SQL statement. That leads to errors on model migration.

I fixed this error by checking the data type of the default value and adding parantheses around it if it is a text type.
