sqlite driver adding block integrity checking to finalize_file()
A better return json to explain gaps and overlaps
need file_size to validate the whole file in finalize_file
1.verify the begin and the end of a file. 2. unit tests
register a block to BLOCKS meta should not overwrite existed one, if user need replace, the user should unregister then re-register
Merge remote-tracking branch 'repo/master' into 9_finalize-check-gap-overlaps
register a block to BLOCKS meta should not overwrite existed one, if user need replace, the user should unregister then re-register
unregister blocks before renew their information
9_finalize-check-gap-overlaps: Remove temp table, work on query return directly, for gap/overlap checking
pep8 fix
Removes superfluous improts from cassandra test
Merge pull request #16 from painterjd/cleanup_cassandra

Removes superfluous imports from cassandra test
B-32-block-put-abs-url: add a test case on None block_id
9_finalize-check-gap-overlaps: new merge from master, add check to cassandra drv
9_finalize-check-gap-overlaps: finalize_file returns are verified
9_finalize-check-gap-overlaps: fix json module
9_finalize-check-gap-overlaps: exception 413 on gap n overlap, caller needs catch exception
9_finalize-check-gap-overlaps: simpler checking coding and to reformat err msg
Ads OverlapError and GapError

Adds two exceptions to reflect errors that can occur during a file
finalization process.
Merge remote-tracking branch 'xuan/9_finalize-check-gap-overlaps' into fix_cassandra_overlap