Rename unit_length attr_accessor to unit_side for consistency with the
shape counterpart
Pass unit side configuration to shape constructor from game strategy
configuration
Change implementation of tetris map to access it more conventionally
Test freeze shape method with more meaningful parameters.

The method was having a bug because the test parameters had the same x
and y values
Add parse_color method to shape class.

This adds capability to have more colors for a shape
Generate shapes with random colors
Generate random shape x for a shape based on its width
Exit the game if there is no space to generate a shape