Initial refactor for __rvm_select()
fix detecting if flags/patches are applied for the named rubies warning, update #2399
extend max-time for file_exists_at_url to avoid intermittent errors for finding remote files, fix #2399
Merge pull request #2393 from wayneeseguin/selector-refactor

Refactor __rvm_select (possibly the entire selector)
code formating for #2393
split __rvm_select into subfunctions, update #2393
silence downloading patches
convert rubinius low memory error to a warning and move it further in the process, fix #2400