more logic to not do extra processing. A lot more comments to explain whats happening.
(1) returns false on 3 timeouts now. (2) more code standards..
small bug fix.
more improvements and bug fixes
all networking now happen in a separate thread. However there is no sync between the producer (tile data being generated) and consumer (tiles being rendered). Can work on a producer-consumer sync when the time is right.
all networking now happen in a separate thread. However there is no sync between the producer (tile data being generated) and consumer (tiles being rendered). Can work on a producer-consumer sync when the time is right.
Merge pull request #3 from tangram-map/curl-async-fetching

1. Implements libCurl multi interface with select() and file descriptor setting and error checking.
2. Implements relevant timeout:
    2a. Timeout for not able to contact the service
    2b. Timeout for not able to retrieve the data in 1 sec from the service.
3. Implements simple std::thread for fetching of tiles from service.
4. Implements CheckDataExists for DataSource class.