Greatly expand the components overview in Overview.md
Greatly expand the components overview in Overview.md

Summary: See title. This is create a big flat mess, which I may clean up in a follow on to highlight the biggest and most generally useful libraries.

Reviewed By: fugalh

Differential Revision: D2902152

fb-gh-sync-id: 028633448ab97f47a3419f31fa58c79b77a89e52

floxard/folly,brunomorishita/folly,facebook/folly,facebook/folly,Orvid/folly,Orvid/folly,mqeizi/folly,charsyam/folly,facebook/folly,charsyam/folly,rklabs/folly,mqeizi/folly,mqeizi/folly,Hincoin/folly,floxard/folly,mqeizi/folly,charsyam/folly,rklabs/folly,Orvid/folly,facebook/folly,rklabs/folly,rklabs/folly,Hincoin/folly,floxard/folly,charsyam/folly,brunomorishita/folly,Hincoin/folly,brunomorishita/folly,rklabs/folly,brunomorishita/folly,floxard/folly,facebook/folly,brunomorishita/folly,Hincoin/folly,Orvid/folly,floxard/folly,Hincoin/folly,mqeizi/folly,Orvid/folly