Fix doc installation in "vim" Makefile task.

Copy README to 'doc' subdirectory and mark the header with asterisks.
The latter appears to be required for `:helptags` to pick it up.
support both HTML (with) and XML (without HTML specific behaviour)

* new options '--xml' and '--html' (default) added
* XmlDialect added without shortcuts, fill attributes and so on
* Vim: ftplugin 'xml' added as symlink
* Vim: call sparkup.py with the filetype as argument
* so my XML can have <area> tags without attribute filling
* yet my HTML still can
Add an option to indent with tabs instead of spaces

I can't see an easy way to get this into the shortcuts and have no run
the unit tests. Please excuse my python inabilities.
Remove the button synonym

Remove button as a synonym for an input with type button. Button is a
perfectly good element in it's own right.
Turn the spaces in shortcuts into tabs

This will probably break the unit test and is not adjustable by
options. Not recommended.
Always use noremap to avoid recursion problems
Fix for remapped <Esc>

If you've remapped <Esc>(To <nop>, for instance) then the insert mode
mappings fail, ouputting the whole command(:call <SID>Sparkup()) into
the current document.
Merge branch 'tqmz/master'
support both HTML (with) and XML (without HTML specific behaviour)

* new options '--xml' and '--html' (default) added
* XmlDialect added without shortcuts, fill attributes and so on
* Vim: ftplugin 'xml' added as symlink
* Vim: call sparkup.py with the filetype as argument
* so my XML can have <area> tags without attribute filling
* yet my HTML still can
/env python -> /env python2

On Archlinux python is linked to python3.
Do not add normal mode mappings for Vim.

Closes #35
Improve mapping for Vim, using <Plug> maps>

Add redirection through <Plug>SparkupExecute and <Plug>SparkupNext and
check if mappings are defined for them before assigning default maps.
Fix doc installation in "vim" Makefile task.

Copy README to 'doc' subdirectory and mark the header with asterisks.
The latter appears to be required for `:helptags` to pick it up.
Use `inoremap` for calling Sparkup{,Next}().

This will make the mapping work properly with e.g.
`noremap : .`.

See https://github.com/rstacruz/sparkup/pull/40#issuecomment-1202903
Use `return` instead of `finish` in a function
Use full path for s:sparkup

When determining `s:sparkup` the whole path should get used.
`findfile()` might return a relative path, so we use `fnamemodify(..,
':p')` to transform it into an absolute path.
Mention sparkup.py besides sparkup in the error message
Unset s:sparkup in case of error

Besides allowing for a re-detection on next invocation, it will prevent
and error from trying to execute an empty command.
/env python -> /env python2

On Archlinux python is linked to python3.
Merge pull request #72 from Profpatsch/master

/env python -> /env python2