Allow for rangeblocks in block() via $range parameter
Followup previous: tidy range condition
Change error condition for returning false

Previous condition does not capture "alreadyblocked" error as API
still returns the details of a block, like it does on success. The
API distinguishes by setting an error parameter, so we should just
check for that.
Merge pull request #70 from Jarry1250/blocking2

Allow for rangeblocks in block() via $range parameter