make it so active list group items aren't dependent on an <a> tag. Drop background-clip and background-size mixins since they have no prefixes anyway. Added button-size mixin. Newfangled input and button group sizing

BS3 commits acdbe738517b592d8a92fb7c94da09c20d5e65f9,
55cfa8d38f71623aaa5e2aae97b483af60650910,
ddd13dc100db6a51dac927bcc884e1a8de5b35c0,
a78c8d9c04e83a22d6eebc2e3d54cb2ccf6b614c
inline forms now require use of .form-group for proper alignment of all form controls

BS3 commit f662dff6e9c52770511e5f674579a27eeac85549
fixes 9266 manually on account of list group file reorganization. Aria role search instead of form. update to rename rc2. Newfangled input and button group sizing. _includes/social-buttons.html: escape ampersands in URLs to fix HTML validation error. social-buttons.html: drop 'px' from height+width attrs per HTML5. add alt text to thumbnail <img>s. add alt text to media object <img>s

BS3 commits 5e73cc90d9104dc251fba5dcaf203523785ee9a5,
657c19f94343e2349eef3e8640baaf7b21562fb3,
a09531a40e8d892b49e5b3b630fa53f1926a4286,
a78c8d9c04e83a22d6eebc2e3d54cb2ccf6b614c,
7f8f1ca65e6d908da5dce4536c3d4d5f055dc6a7,
e6e60d325ca69010f1334283140dfd2a2ee3cc74,
5b9717ef67e679d3ae2a70023d042136db00ce71,
598f811fa0838ba6153e07862621f13e6c877ca4
Add missing aria-hidden attribs to close buttons. inline forms now require use of .form-group for proper alignment of all form controls. copyedit media queries docs added in aefed0a. update to rename rc2. _includes/social-buttons.html: escape ampersands in URLs to fix HTML validation error. social-buttons.html: drop 'px' from height+width attrs per HTML5. fix ID of <select> in fieldset[disabled] example. Validation states docs: fix closing tag. add alt text to <img>s in Images section of CSS docs

BS3 commits 1f745176d4e667fd75a492509a4e08ca54af07ae,
f662dff6e9c52770511e5f674579a27eeac85549,
f5b14997766de3a7481936e669fba03e2a10241d,
a09531a40e8d892b49e5b3b630fa53f1926a4286,
7f8f1ca65e6d908da5dce4536c3d4d5f055dc6a7,
e6e60d325ca69010f1334283140dfd2a2ee3cc74,
1c64c8f43bece9a2e97be510266c48969dca0963,
4876a3a7162ea2be8b1c316fde1039d22a6b64d3,
520bc8cf37c0b5424427d22ecc3190b6abf461d7
update to rename rc2. _includes/social-buttons.html: escape ampersands in URLs to fix HTML validation error. social-buttons.html: drop 'px' from height+width attrs per HTML5

BS3 commit a09531a40e8d892b49e5b3b630fa53f1926a4286,
7f8f1ca65e6d908da5dce4536c3d4d5f055dc6a7,
e6e60d325ca69010f1334283140dfd2a2ee3cc74
update to rename rc2. _includes/social-buttons.html: escape ampersands in URLs to fix HTML validation error. social-buttons.html: drop 'px' from height+width attrs per HTML5. mention 9282 in docs browser section

BS3 commit a09531a40e8d892b49e5b3b630fa53f1926a4286,
7f8f1ca65e6d908da5dce4536c3d4d5f055dc6a7,
e6e60d325ca69010f1334283140dfd2a2ee3cc74,
3f2408f9e8cbdf359fdc587a8b463c06860162f4
update to rename rc2. fix spelling. _includes/social-buttons.html: escape ampersands in URLs to fix HTML validation error. social-buttons.html: drop 'px' from height+width attrs per HTML5

BS3 commits a09531a40e8d892b49e5b3b630fa53f1926a4286,
e245bffe8c951a0bba2bb045fb6bbe674d471693,
7f8f1ca65e6d908da5dce4536c3d4d5f055dc6a7,
e6e60d325ca69010f1334283140dfd2a2ee3cc74
Added Dropdown JS plugin events to docs. Add missing aria-hidden attribs to close buttons. update to rename rc2. Javascript > Alert should use danger not error. _includes/social-buttons.html: escape ampersands in URLs to fix HTML validation error. social-buttons.html: drop 'px' from height+width attrs per HTML5. add alt text to carousel <img>s

BS3 commits 0c879d3ece1a6b1f70d1117a79876554e2ee6479,
1f745176d4e667fd75a492509a4e08ca54af07ae,
a09531a40e8d892b49e5b3b630fa53f1926a4286,
c3c02183790f689cfb3adccf28c0dbdb949b7904,
7f8f1ca65e6d908da5dce4536c3d4d5f055dc6a7,
e6e60d325ca69010f1334283140dfd2a2ee3cc74,
df59ecc9c40534e34a140cb5a00607c50b2b500c