Clarify doc for loading custom extensions
minor doc fix: s/various some/various/
Customizes tabline appearance: type, close button

This commit adds a couple of new settings so that it's possible to hide
the tab type (all the way to the right) and the symbol which represents
the close button.

The settings and their defaults:

let g:airline#extensions#tabline#show_tab_type = 1
let g:airline#extensions#tabline#close_symbol = 'X'
Merge pull request #464 from emilyst/customize-tabline-close-and-type

Customizes tabline appearance: type, close button
Merge pull request #466 from Pychimp/master

Improvements to Sol and Luna themes
Merge pull request #442 from blueyed/doc

Minor doc fixes
filter() result error
My fault, it's a transferred error, add a '\' that' works fine.
Merge pull request #467 from xinleibird/master

filter() result error