Script tests: script_valid.json passes again

also add script_invalid.json which doesn't pass yet

`cabal test` hangs for some reason
Script tests: skip test_invalid.json
Merge pull request #57 from OttoAllmendinger/script-tests

Fix script tests
Adding support for base < 5
Merge pull request #58 from plaprade/base5

Adding support for base < 5
Simplify Mnemonic and remove dependency on ICU
Merge pull request #60 from xenog/simplify-mnemonic

Simplify Mnemonic and remove dependency on ICU