Update copyright notices in all places

- Implements new format "Copyright 2011-xxxx Twitter, Inc.", which resonates well with our History page and more accurately reflects the copyright status of the repo
- grunt dist to update all the files
missed a file

X-Ref: https://github.com/twbs/bootstrap/commit/7fcfe61f4da41356b2ae974ad20536db0d74e83f
duh, missed one more file

X-Ref: https://github.com/twbs/bootstrap/commit/7fcfe61f4da41356b2ae974ad20536db0d74e83f
Merge branch 'master' of https://github.com/twbs/bootstrap