added CSS so that Facebook widget would show properly in Firefox.
make input fields use the nice bootstrap-style placeholders
always show run button for activecode blocks
remove :nopre: param from activecode blocks (issue #177)
replace code:: directive with sourcecode:: (issue #171)
Merge pull request #181 from isaacdontjelindell/issue-177-nopre

Remove :nopre: params; replace code:: directive
Merge pull request #180 from isaacdontjelindell/bootstrap-tweaks

Visual tweaks