Update OOjs UI to v0.1.0-pre (49b64bdba7)

New changes:
c82b429 Work around position: fixed; bug in Safari
9e1432e Split out isPending, pushPending, popPending, etc. into PendingElement

Change-Id: Ifd213123adfc9c96de2f16379c8ed3d706c210f8
Merge "Update OOjs UI to v0.1.0-pre (49b64bdba7)" into wmf/1.24wmf21