Add a few useful utilities, and fix a typo-bug.

Summary:
This was based on my most recent install of my new linux desktop.  I
added instructions to install chrome, and to install svn (needed by
one of the pip install clients, and will also be needed by git-svn,
etc).

I also fixed a typo in the kcachegrind install instruction.

I had no luck with the gem install bundle' command in setup.py, so I'm
tempted to just apt-get install ruby-bundle on linux, but I think the
problem may be limited to me, because of some weird umask I have, so
I'm leaving it be for now.

Test Plan:
Ran
   make
in khan-dotfiles directory on my new linux machine, and had it
complete without error.

Reviewers: chris

Reviewed By: chris

Subscribers: alan

Differential Revision: http://phabricator.khanacademy.org/D7463