Do use elpa deps if there are no el-get :depends

* methods/el-get-elpa.el (el-get-elpa-install-1-package): rename to
el-get-elpa-install-package, take another argument have-deps-p. Only
call package-download-transaction directly if have-deps-p.
(el-get-elpa-install, el-get-elpa-update): el-get-elpa-install{-1
=>}-package name change and new arg.