BUG: handling of empty/garbage messages. parsers return empty dataframe
and decode function does not append them.
add tests for no/garbage data messages
BUG: Incorrect handling of completely empty returns from url request
BUG: Improve empty dataframe handling
replace try/except with simple if/then to avoid capturing non-related errors
Merge pull request #74 from twdb/fix/improve-twdb-parsers

Fix/improve twdb parsers