* created autoload/vundle/compat.vim: "compatibility" module
    (implements functions not available in previous vim versions);
    (code taken from my previous commit in 'autoload/vundle/config.vim',
    then modified and extended);
  * added compatibility function for shellescape();
 * autoload/vundle/config.vim: tidied up so that it's a bit closer to
    the file upstream;
  * (previous commit) but added a few performance improvements (avoid
     unnecessary calls and/or operations);
 * altered other scripts to use 'vundle#compat#*()' functions instead of
    those not necessarily available in previous vim versions;

Certain wildignore values prevented the various logs from being
viewable.

Fixes #249

inspired by
https://github.com/gmarik/vundle/pull/228 and
https://github.com/gmarik/vundle/pull/172

Vim patch #445 changed shell escaping and introduced incompatabilities for vundle.
Now vundle only escapes joined commands with double quotes on windows when shellxquote is not set to '('.
This workaround closes https://github.com/gmarik/vundle/issues/146 - the mentioned workaround
is no longer needed, but it does not break a vim configurations which contains "set shellxquote=".

DRY shell escaping and modified (hopefully) all relevant places.

The codepath does not appear to have been tested; mv on Win32 is move,
and substitute has 4 arguments instead of 3.

- add /d switch to cd command to perform drive change
- enclose joined commands with quotes

Instead of creating a vundle_update tag to compare changes between update
and HEAD we now use the output from `git pull` to get initial/updated shas.

Distinction between `new` and `updated` simplifies the process
of adding a bundle to the updated_bundle list.

If the Bundle is hosted on GitHub include link to compare the commit range
visually on GitHub.

Keeps track of the current commit with a vundle_update tag before
perfoming an update and adds all commits pulled in the update to a
Changelog accessible via pressing 'u' after BundleInstall! completes.

- closes #64

- closes #110

Prevents the user from having to type a space before the search term.

- closes #80

- use `redraw` instead `redraw!`
- closes #90

- to avoid accidental removal

- so it better reflects the content

- do not clutter up ~/

- not sure if there's a need for log file in predefined location
- installer is verbose enough to signal errors

- to avod error when deleting nonexisting buffer

- batch process just iterates through the lines and calls specified
action
- individual actions give visual feedback aswell
- allow Helptags command as a part of installation process

- merge with view()
- no need for having both

- log is global array so log can be viewed any time
- log gets written to a defined location ~/.vim-vundle/vundle.log
- TODO: write log changes as they happen

- TODO: refactor: extract common code

- Bundles is not a good name for search
- BundleSearch undeprecated
- TODO: repurpose :Bundles cmd

- blows up otherwise for default vim on SnowLeo

- ! is error
- . is up-to-date
- * is updated

- instead writing to file and opening it
- faster and has nicer status name

- TODO unify

- as a cleanup
- TODO: make ESC or CTRL-C break installation

- otherwise may conflict with user preferences
- closes #68

- wget only
- curl preserves content with --fail switch