Remove unused script_dir setting

script_dir was only needed for PostGIS 1.x installs
Handle add_index with nil options

Fix #60 regression
Version 2.0.2
Travis: test against ruby 2.1.2
Add version 2.0.2 history [ci skip]
Update column migration method to correctly set null: false

  * Update `MainAdapter#create_table` to execute `change_column_null` if
    the column is set to null: false