Added smallinteger

Added smallInteger detection to avoid generating:
$table->('field');
Moved index declaration, added some check

Moved index declaration after attribut declaration to avoid syntax error : Key column 'whatever_index' doesn't exist in table

Added some check when there are no table in db that would fail.
Moved index declaration, added some check

Moved index declaration after attribut declaration to avoid syntax error : Key column 'whatever_index' doesn't exist in table

Added some check when there are no table in db that would fail.
Merge pull request #6 from Spir/master

Added smallinteger