Add fixed color Id for each piece shape

* Color id is piece shape id + 1 as 0 is an empty spot
Board now has different numbers for taken spots that relate to a color

* Refactor tests to reflect color changes, expect piece.getColorId()
  instead of expecting 1 for taken spots
Update #movePieceRight and #movePieceLeft overlapping tests

* Pieces now represent different numbers on the board (related to colors)
* Tests were passing because the column forced was valued 1
* Update #isPieceOutOfBoundaries to ignore the value of a taken spot
  (0 is false, all other numbers/colors are valid)
Add colors to the pieces

* Colors follow Atari tetris colors http://en.wikipedia.org/wiki/Tetris
* Plain colors are ugly and hurt my eyes
  use colors from http://flatuicolors.com/ instead
* Each piece has a class of 'full' + #colorId() and
  CSS takes care of painting it
Adjust Tetris layout

* Increase Board size to 269px
* Increase Pieces to be 25x25
* Define board grid color with a lighter color
* Set pieces border to a darker color to give contrast
* Add 'piece' class to each one of the actual pieces not the border grid
Merge pull request #4 from brunops/add_colors

Add colors