add baselayer toggle, close #120
add title tags to source view map controls
hide baselayer toggle by default
remove unnecessary space-bottom
Merge pull request #264 from mapbox/baselayer-toggle

Baselayer toggle
add source docs
more work on docs, ui clarifications
docs adjustments
clarify docs
add help shortcut
update shortcuts
clarify docs note
baselayer on by default, if set (closes #268)
docs improvements
add source local/remote tag to settings
Merge pull request #266 from mapbox/source-docs

First draft of source docs
remove redundant local/remote label
remove 'm' icon now that we have more explicit local/remote tag
style pass, consistification
consistent treatment of close buttons