Fix current tagbar tag segment

Closes #139.
Fix grammar error in docs

Thanks to @cerson.

Closes #147.
Fix path styles

- Fix short path style when autochdir isset
- Fix full path style

Closes #144.
Revert "Add aurum segment"

This reverts commit d3916d32a0975eb9f1fbd5206a7c9130e5471915. The reason
why this commit is being reverted is that it adds a dependency on Frawor
which is yet another plugin loader. The segment should be rewritten to
not depend on this plugin.

Conflicts:
	autoload/Powerline/Functions/aurum.vim
Remove slashes from Syntastic segment

Closes #158.
Create temporary fix for Tagbar segment

This update adds a wrapper function that checks if Tagbar is loaded
before trying to call `tagbar#currenttag()`. Unfortunately this only
works *after* Tagbar has been opened, so the Tagbar/current tag segment
will be empty until Tagbar has been opened for the first time.

Refs #152.
Refs majutsushi/tagbar#77.
Update troubleshooting info for #51
Update troubleshooting info for #159
Revert "Create temporary fix for Tagbar segment"

This reverts commit 5948dd5bc28cf4dda75d8532fe4e35b1722353c0.
Defer autocmd creation until all plugins are loaded

This update ensures that Powerline's autocmds aren't created until vim
has loaded all plugins and settings, to avoid errors with plugins that
are loaded after Powerline. The VimEnter event is used to accomplish
this.

Closes #152.
Refs majutsushi/tagbar#77.
Change virtualenv function call

Closes #165.
Correct capitalization of Vim and Unicode in the docs

Thanks to @dougireton.

Refs #173.
Add usage examples and better explanations to docs

Thanks to @dougireton.

Refs #173.
Closes #168.
Allow configurable mode names

Closes #175.
Closes #176.
Add tagbar:fullcurrenttag segment

Closes #180.
Allow users to customize Ctrl-P's statusline

This lets you disable focus, prev, next:
	let g:Powerline#Segments#ctrlp#segments#focus = ''
	let g:Powerline#Segments#ctrlp#segments#prev = ''
	let g:Powerline#Segments#ctrlp#segments#next = ''

Closes #185.
Cache the current filepath when cwd == .

When editing a file in the current working directory, cache the filepath
just like when outside the cwd. (If b:Powerline_filepath isn't set, the
filepath isn't cached and vim recalculate everytime it draws the
statusline.)

Still doesn't cache when the filepath is empty.

Refs #179.
Refs #189.
Update the filepath when the cwd changes

The g:Powerline_stl_path_style == 'relative' option requires the
filepath to be updated everytime the cwd changes.

Store the cwd and if the stored value's different from the current,
clear the cached filepath.

Closes #179.
Refs #189.
Make relative path style also relative to home

Update g:Powerline_stl_path_style == 'relative' to be relative to home
(in addition to relative to the cwd) just like the %f statusline item.

Closes #190.
Include both column and virtual column in line segment

Closes #169.