Add question: 'AskChoice'

AskChoice takes an optional question 'Text', and  a list of 'Choice'
values associated with a value of type 'a'. The client is responsible
for displaying the question and choices and inquiring an answer.
Add card 'War Priest of Thune'

This is the first card to make use of the new 'AskChoice' question.
Merge pull request #46 from gseitz/war_priest_of_thune

Add card 'War Priest of Thune'
Fix CLI display of the colour Blue.
Merge pull request #48 from gseitz/fix_cli_color_display

Fix CLI display of the colour Blue.
Angelic Benediction: Adhere to the 'may' in the card text.

The card text says "you may tap target creature", but the implementation
would always result in tapping the  target creature. This can make a
difference if only Angelic Benediction and Guardian Lions are on the
battlefield, Guardian Lions attacks, yet you want to keep it untapped 
(eg. for blocking potential opponent's creatures with Haste).
Merge pull request #50 from gseitz/angelic_benediction_fix

Angelic Benediction: Adhere to the 'may' in the card text.
Add reveal functionality + Lilian's Shade