intIn
Usage: intIn(start, end)
Returns a spec that validates ints in the range from start (inclusive) to end (exclusive).
Example:
const s = require('speculaas');
// Define range of a single byte
s.def('::oneByte', s.intIn(0, 256));
s.isValid('::oneByte', 0);
// true
s.isValid('::oneByte', 256);
// false
s.isValid('::oneByte', 512);
// false