Create function to migrate legacy proposal files

[mattstratton]

• Read in source directory
• Determine city and year from source directory
• Parse out title of talk and make it pretty
• Make a "space happy" version of the title URL (using %20 for spaces) and use this to construct the alias
• Parse out all the non-frontmatter stuff
• Write the stubbed out frontmatter to the proper destination directory

[mattstratton]

No longer needed