Fix handling of broken connection to Piksi.
Merge pull request #78 from gsmcmullin/python-sbp-disconnect

Fix handling of broken connection to Piksi.
Fix direction in SBP comments
Merge pull request #80 from cbeighley/fix_sbp_comments

Fix direction in SBP comments
Merge remote-tracking branch 'upstream/master' into usart_rework
Update documentation comments.