Ignore strings when indenting
Tentative :Play command, fetching code from the playground
WIP More flexible :Fmt

This one should be easier to use automatically upon saving. The
interface might be better as `:Fmt silent write`, though.
Minor fixes and notes
Set all did_ftplugin flags

Without these, the built-in go stuff overrides the bundled one. It
should be changed upstream, but for now, this'll do.