Fixes fa-font-path value for netdna bootstrap CDN
Closes #2193
Fixed hdd icon id
Closes #2208
Fixed version reference in get started

Closes #2218
Fixes fa-stack alignment
Added failing test case
Closes #2213
Added link to 3.2.1 docs in the footer, just like Bootstrap
Closes #2200
Bumped version number to 4.0.1
Added missing !default in scss variables
Closes #2231
adding upgrade wiki page to documentation
adding pointer to rtfm for syntax changes
Updated the icon count in the readme
Merge pull request #2249 from GrahamCampbell/4.0.1-wip

Updated the icon count in the readme
Proper example for bootstrap input groups
Closes #2241
Merge branch '4.0.1-wip' of github.com:FortAwesome/Font-Awesome into 4.0.1-wip

* '4.0.1-wip' of github.com:FortAwesome/Font-Awesome:
  Updated the icon count in the readme
  adding pointer to rtfm for syntax changes
  adding upgrade wiki page to documentation
making 3.2.1 docs more prominent, adding test for FA 4.0 + BS 2.3.2