q01 - last element

start working on 99 haskell problems
q02 - done
q03 - done
q04 - done
Merge branch 'master' into h-99
question 05
q-05 - some refinement
q-06 - done
amb-eval - lambda
question7 - done
rename question -> problem
my-eval - expose if-xxx
amb-eval - impl if-expr
amb-eval - sequence
exercise 1 - done
exercise 2 - done
nucleotide-count - version 2

better to have `show c` to handle char pretty printing
remove unnecessary import
point-mutation - version 2

`==`, `not` => `/=`, `id`
amb-eval = definition handling