Squashed 'bundle/vim-airline/' changes from 310331c..be6e4d6

be6e4d6 check background of groups to determine transition. resolves #599.
727192a refactor builder and reduce state across multiple calls
256dec6 detect changes to tabline config variables after init. resolves #636
246c217 Merge pull request #631 from rkannan82/master
3e0b547 Merge pull request #628 from freeo/master
328016c Exclude INFO from error/warning count.
82a4ebb Theme kalisi: Added 256 term colors, several changes
64b9ae1 Merge pull request #618 from rkannan82/master
616dace add small section about performance to readme
37ddb6e Merge pull request #622 from spacelis/master
c85ce90 Merge pull request #619 from bchretien/master
7c4bf0a Make tabline's left separators customizable as right separathers.
23b452d themes: fix GUI murmur theme.
84c242a Display warnings only when there are no errors messages.
0bc3a21 Merge pull request #614 from Pychimp/two-themes
258817f Update raven.vim
53e765a Merge pull request #582 from Pychimp/two-themes
51c788a Merge pull request #613 from meonkeys/patch-1
b16870f Added theme support for console vim
6feec73 README: fix link to powerline font install docs
825a048 Merge pull request #603 from kballard/part_condition_special_char
908f031 Handle special characters in part conditions
4dab934 improve buffer index mode and fix usages where there's overflow
8421f03 Merge pull request #598 from wesQ3/pr
50c9ea8 Merge pull request #589 from paulhybryant/master
ae472d6 Add buffer_idx_mode to vim-airline. Update documentation. Keep buffer index-id map a script scope variable.
3eef719 Merge pull request #595 from mseabold/upstream
d647568 add windowswap extension
a5e5d8a Tabline protect against missing palletes
3f3ae44 Merge pull request #591 from igorpetrovcom/tabline-close-button-flag
bfd160a Tabline: Highlight unselected modified buffer
6e58654 Tabline close button flag added
47fd635 Added two themes

git-subtree-dir: bundle/vim-airline
git-subtree-split: be6e4d6dd63a49132fc758643bb393a7f41f8b82
Merge commit 'bf4992f592adb416fb1797e8e911f38088ed888b'