Checks whether scroll-bar-mode is defined before calling it.

* The terminal version of Emacs 24.1.50.1 does not load
  scroll-bar-mode and hence throws an error when loading
  powerline. This patch only stops the error from appearing.
  However, the modeline becomes totally green and unusable
  in the terminal. That needs fixing.
Fixes typo in the readme.
Use `format-mode-line` to convert mode-name data into a string
Fix html-mode going blank by adding format-mode-line to mode-name. Credit: @Okasu
Add @jart, @Okasu, and @prakashk to AUTHORS file.
Add Hans Engel to AUTHORS list.
Merge pull request #14 from hans/master

Format `mode-name` with `format-mode-line`
Merge pull request #9 from gorakhargosh/master

Checks whether scroll-bar-mode is defined before calling it and fixes typo.
Add Yesudeep Mangalapilly to AUTHORS list.
Merge branch 'master' of github.com:jonathanchu/emacs-powerline
Merge pull request #8 from filsinger/ed2cdfa421e3782da126bcae8af6f6657aac4444

powerline.el has a requirement on cl
Add Jason Filsinger to AUTHORS list.
Update email address in AUTHORS file for @gorakhargosh.
generate arrows with parameterisation
arrow size dependent on mode-line height
Merge pull request #19 from katspaugh/master

Generate arrow images of variable size
Add @katspaugh to AUTHORS file. Thank you!
Merge upstream from jonathanchu/616fbf7980c488530c95a5013c345c8aca3da23d