add score keeping

track and display the score
squashed merge of lots of changes

added:
  score keeping
  game over detection
  restarting the game
  coloring of tiles
  better randomisation

also reorganised some things

Squashed commit of the following:

commit 0c2f299f4fe02e7fd9afb3b4268ea8bcf0e31183
Author: notnew <notnew@no.email>
Date:   Sat Apr 12 15:52:30 2014 -0500

    improve tile generation

    when generating 2 tiles from a single random number, don't always
    generate them to be the same tile (a pair of 2's or a pair of 4's)

commit ab38a01ea3ed64856a645a8c088caf99768c51a4
Author: notnew <notnew@no.email>
Date:   Sat Apr 12 15:27:15 2014 -0500

    improve display

    nicer looking layout for score and restart button
    add start screen

commit 41372cd3e9653b729cf8f88dc886de52456e6686
Author: notnew <notnew@no.email>
Date:   Sat Apr 12 14:55:11 2014 -0500

    allow restarting of game

commit 40aef8234000bf5ca1ee927b46d8428a17c6fe38
Merge: 46f9097 7dddbd8
Author: notnew <notnew@no.email>
Date:   Sat Apr 12 14:10:01 2014 -0500

    Merge branch 'animate' into restarts

    mostly for Event type, but rowPoints is also a little cleaner
    dropped all the time based stuff

    Conflicts:
    	2048.elm

commit 46f90971487fb7b9fd6daa5270574145c15d9bc8
Author: notnew <notnew@no.email>
Date:   Sat Apr 12 13:52:14 2014 -0500

    upgrade from elm 0.11 to 0.12

    only very minor changes (some names in Text module)

commit b4c20ea8db2deb9ad06537825e8123fa11e29ef3
Author: notnew <notnew@no.email>
Date:   Sat Apr 12 10:38:41 2014 -0500

    refactor display code

commit 7dddbd8bd842afa00aabdb54ecc912c31f2a2b56
Author: notnew <notnew@no.email>
Date:   Fri Apr 11 15:26:12 2014 -0500

    add simple animation

    color newly spawned tiles green, then change them to normal color
    after a short time

commit 29bd33938b3d605d8f73caf87d69d1a7d02b1102
Author: notnew <notnew@no.email>
Date:   Fri Apr 11 14:00:54 2014 -0500

    add Event type

    to separately track sliding move events (generated by keyboard) and
    clock ticks (for animations)

commit 99ef9aa3933060f490dce17d5b76b51e4a7cd0e9
Author: notnew <notnew@no.email>
Date:   Fri Apr 11 13:35:00 2014 -0500

    cleanup, organize code better

commit c374c931a99fb5b29955c36869d60e492c6584a3
Author: notnew <notnew@no.email>
Date:   Fri Apr 11 13:24:02 2014 -0500

    detect game over state

    and display game over message

commit 9a25edbf1432614a9c5d223c512b31eacd04152e
Author: notnew <notnew@no.email>
Date:   Fri Apr 11 02:08:44 2014 -0500

    add color

commit 5513d47292d61ae667b46fc35b1dbf6b4965c95d
Author: notnew <notnew@no.email>
Date:   Fri Apr 11 01:15:05 2014 -0500

    use ADT to track keyboard directions