Bug fix: Don't persist &go and &gfn when !has('gui') (issue #54)

Issue #54 on GitHub:
  https://github.com/xolox/vim-session/issues/54
Changed to retain server name when calling VimRestart
Moved servername fix to apply to other platforms than windows
Merge pull request #59: Make :RestartVim retain server name

See pull request #59 on GitHub:
  https://github.com/xolox/vim-session/pull/59
Bug fix: Disable Vim's special handling of initial, empty buffer

See issue #28 on GitHub:
  https://github.com/xolox/vim-session/issues/28
Internal refactoring: Merge s:get_name() and xolox#session#find_current_session()
Internal refactoring: Replace s:select_name() with xolox#session#prompt_for_name()
Working on inline function documentation
More inline function documentation :-)
Bug fix: Re-implement Vim's special handling of initial, empty buffer

See issue #60 on GitHub:
  https://github.com/xolox/vim-session/issues/60

This is a follow up to my recent changes for issue #28:

  Bug fix: Disable Vim's special handling of initial, empty buffer
  https://github.com/xolox/vim-session/issues/28