Update dash dependency 1.8.0 -> 2.9.0
Use dash 2.4 instead.

This is what flycheck uses
Use newest stable flycheck
Use newest stable popup library version on melpa stable
Sort usings
test
Epic test
Revert "Epic test"

This reverts commit 4027cb7ffbaa6fbf38a52b341c05168268df4b33.
Test removing other dependencies besides dash
Up dash to 2.4 -> 2.9
Try newest dash version
Add test for the melpa build script
Run melpa build script in a sandbox

The sandbox command is melpa's "make sandbox" command ripped
Improvements to melpa build test
Include testing recipe
Fix using testing melpa recipe too late
testing
Update dash
Remove melpa stable
Revert "Test removing other dependencies besides dash"

This reverts commit 85e261d28d0869bb263ab5972a16a24d747aa9c7.

Conflicts:
	omnisharp.el