Improve yasnippet

[tuhdo]

• Allow a snippet to wrap around a selected region when expanded: A user
  can select a region, press 'C-x C-x' to go to the original mark and
  run yas-expand to wrap the selected region in expanded snippet.
• Reindent spacemacs/load-yasnipppet.
• Allow hippie-expand to expand snippets as well. May replace TAB in
  the future.

[syl20bnr]

I finally merged it but I don't understand the wrapping feature, can you do a GIF to show it in action ? :-)

Anyway thank you !
Cherry-picked into develop branch, you can safely delete your branch.

[tuhdo]

@syl20bnr Here your gif is:

To try it:

• Type any snippet keyword before a region you are going to expand.
• Set mark with C-SPC C-SPC.
• Select a region.
• Go back to the mark earlier with C-x C-x.
• Press TAB.

Now the expanded snippet wraps around the region, i.e. a for loop wraps the selected code region in the demo.

[syl20bnr]

@tuhdo That's super cool, thank you ! 👍
Funny thing: to my knowledge it is impossible to do in visual state, but this could be automated with a single key binding I suppose.