remove both fetch_block_transaction_hashes and replace with a single
fetch_block_transaction_indexes (by block hash).

This enforces people to use the block hash instead of height which is safer.
use prefix iterator in for loop as per guide.
import no longer takes a height parameter.
Merge pull request #45 from evoskuil/develop

Update build configuration.
Merge pull request #47 from evoskuil/develop

Travis integration, tied to develop (for now).
Merge pull request #48 from evoskuil/develop

Update attributes for Travis execution.
Don't build unused boost component, propery execute tests.