Fixed issue #33.

Fixed
-----
* Updated the installation instructions to only list the recommended
  ways of installing landlab. For Windows and Mac this is from GitHub
  with the GitHub GUI, for Linux it's from the command line with git.
Fixed issue #33.

Fixed
-----
* Updated the installation instructions to only list the recommended
  ways of installing landlab. For Windows and Mac this is from GitHub
  with the GitHub GUI, for Linux it's from the command line with git.
Merge branch 'fix-issue-33' of github.com:mcflugen/landlab into fix-issue-33
Merge pull request #43 from mcflugen/fix-issue-33

This fixes issue #33.