Fix resetting scoped config defaults

It would write an empty object for the parent key when there were no
other objects in the parent key.

Closes #4175
Merge pull request #4194 from atom/bo-fix-scoped-config-default

Fix resetting scoped config defaults
Update linux.md

Update `git fetch` command to include the prune flag which will remove remote branches that no longer exist.
:arrow_up: language-c@0.31
Merge pull request #4209 from stramel/patch-1

Update linux.md
Listen for middle mouse paste on linux