Update forms example to show sequential form inputs for later testing

BS3 commit d651c01e10cd0f69529e5bcb20f5d1a4b6508c48
Update docs on responsive images and elaborate on IE8 support using Respond.js

BS3 commit df851b40d1accb1c6db44ac77a28c2e76273581b
Update file input to remove height and line-height

BS3 commit a63db4d2f91c056310fc9a24891dbd161672451b
remove useless display:inline-block. Remove commented out CSS. Remove more commented out CSS from forms. Update file input to remove height and line-height

BS3 commits 832fdf9a365689c9d50995b70a1f501c4555901b,
732e4196fb9dc76ce2250edcdc6c1b45bcbe5d2e,
51dfa21009459c98b8d98a63cfc3d2abe29f9017,
a63db4d2f91c056310fc9a24891dbd161672451b