Fix W3C CSS gradients syntax.

The official, unprefixed syntax needs "linear-gradient(to [direction], ...)" notation instead of "linear-gradient([direction-from], ...)" from earlier ones.
https://developer.mozilla.org/en-US/docs/Web/CSS/linear-gradient
Forgot to change the year
Merge pull request #561 from bidtiz/patch-1

Forgot to change the year
Merge pull request #558 from dos1/master

Fix W3C CSS gradients syntax.
Fixes #559 issue with homepage wording
Merge branch 'master' of github.com:Semantic-Org/Semantic-UI
Removes vendor prefixes grid
Fixes form add prompt to be more comprehensive, easier to work with, Fixes #567 #541
Computer breakpoint is now 992 instead of 998 (match bootstrap)
Fixes exact matches to breakpoints returning both devices, i.e 768px screens showing both mobile and tablet. Fixes #527
Fixes #552 Generic ascending/descending icon was overriding some other sort icons. Fixes #552
Builds 0.12.2 release version
Fixes message attached between top and bottom.