Drop background-clip and background-size mixins since they have no prefixes anyway

BS3 commit 55cfa8d38f71623aaa5e2aae97b483af60650910
Renamed btn-pseudo-states mixin to btn-variant for consistency

BS3 commit 3d11e6dedf0174e2124985828f64c6fe68c874f6
Added button-size mixin

BS3 commit ddd13dc100db6a51dac927bcc884e1a8de5b35c0
inline forms now require use of .form-group for proper alignment of all form controls

BS3 commit f662dff6e9c52770511e5f674579a27eeac85549
update to rename rc2

BS3 commit a09531a40e8d892b49e5b3b630fa53f1926a4286
update download_dist for RC 2

BS3 commit 461b05f5b1d75341fd8b98a216c69e2cc33418be
update CDN links to point to continuously-updated build

BS3 commit af2ea581b24bfae28a72275fac000a72e9e4130a
Newfangled input and button group sizing

BS3 commit a78c8d9c04e83a22d6eebc2e3d54cb2ccf6b614c