This commit supports steps 1 and 2 in the new workflow:
1. Change the logic in the daemon to check the github api for the latest release that is not a pre release
2. Change travis to mark all releases as pre release
3. When we are ready to stage a release we push a tag to master. Travis builds the packages and releases them
4. We manually check them
5. Remove the pre release mark when we are happy
This tries to download a small image with a five minute timeout. After this, the bot waits ten minutes and tries again. Any failures get posted to slack.
Put stream downloader options into its own class, and make stream
downloader options global to the stream type rather than specific
to each factory.
Show downloader options in the lbrynet-downloader-gui.
Make a class for downloader option choices, so that the descriptions
can be displayed.
In the console, if there are multiple choices for the download
option, make it a list selected by its index.
Make sure that the ConnectionManager closes properly when some of
the connections fail to open (e.g. due to a host being down)
