Use vim script tern_for_vim to provide javascript editing features

Signed-off-by: Rodrigo Belem <rodrigo.belem@gmail.com>
Replace neocomplcache and clang_complete by YouCompleteMe

Signed-off-by: Rodrigo Belem <rodrigo.belem@gmail.com>
Use <Enter> to select highlighted Pmenu item

Signed-off-by: Rodrigo Belem <rodrigo.belem@gmail.com>