Fix util#is_valid_url for url value None
Merge pull request #50 from larskluge/develop

Fix util#is_valid_url for url value None
blockr API handles missing txes more gracefully
blockr api tweak
fix decimal price
[CounterpartyXCP/counterwallet#372] fix orders for no divisible assets
[CounterpartyXCP/counterwallet#369] block cache for all DEX functions
decimal precision to 8
extend and fix get_markets_list limit
extend and fix get_markets_list limit 2
fix previous commit
[CounterpartyXCP/counterwallet#339] add _block_time in get_last_n_messages
fix previous commit
Merge pull request #51 from CounterpartyXCP/develop

Merge Develop in Master