[Vim] Fire FileType autocmd in all buffers after lazy load

Ensures plug-in functions in all buffers after it is lazily loaded on an
event such as InsertEnter.
[Vim] Refactor transmit.vim into autoloads

Fixes broken alternate file functionality.
[Vim] Autoload fold text function
[Vim] Various fixes to lazy loading

- Use CursorHold instead of BufWritePre to lazy-load Syntastic.
- Revert bufdo autocmd change, which introduces worse problems, since it
  leaves you in the last buffer rather than the original one.
[Vim] Add mappings to set file type