2.0 ~> 2.1 Migrator

This migrator:

1. Creates local copies of imathis/octopress (branch 2.1, or updated master)
2. Copies the appropriate files and directories from the current directory to the new clone ( **HANDLE OVERWRITE CONFLICTS?** )
    - `.git`
    - Plugins which are not present in 2.1
    - `source`
    - `sass`
    - `.themes/* - .themes/classic`
3. Collect configs and write to new config structure
4. Removes the local Octopress installation and replaces it with the new clone and modified files
5. Moves the new clone with the modified files to the location of the old Octopress installation

This should ensure the migration of the current Octopress installation to v2.1.