Ignore Cabal sandbox
ESPL: Strengthen variants of prefix close
Update dependencies in .cabal file
Update lexer to work with Alex 3.x

GHC 7.8 broke the archived lexer module, so it's a good opportunity to
revive the input file. Alex is now required for building; versions
before 3.0 are not supported.

Tested to compile with GHC 7.8.2.
Merge branch 'update-deps' into matching
Add injective modifier to general claims
Implement some missing cases
Model a toy commitment protocol