Tetrogue 1.4 released

Content update with two new features:

• Add the ability to "hold" a piece for later, by pressing SHIFT or C key. 
• Add maps: Each level can now randomly start with structures already present such as: Pyramids, checkers, concrete spikes, caged monsters, and more.
  • There are currently 19 different maps

Other changes:

• Properly center the playing field
• Improve layout of the in-game UI
• Add audio feedback when move or spin is blocked (e.g. moving into a wall)