Minor spelling 

5th bullet point in Features section had the word "colorschemes"

Proposed fix: color schemes
Allow changes to airline_symbols.branch after init

If the user updates the airline_symbols.branch variable later in the vimrc, the value will not update after the initial init.  Since these variables are only used in the get_head() function, I moved them locally within the function to allow evaluation on each instance.
Merge pull request #412 from gabriellim/patch-1

Minor spelling
Merge pull request #413 from ralesi/patch-1

Allow changes to airline_symbols.branch after init
Add deeper netrw support, including Git branch head and netrw sorting
options
Merge pull request #418 from ralesi/netrw

Add deeper netrw support, including Git branch head and netrw sorting
happy 2014
account for possibilty of branch extension unavailable. resolves #419.