chore(README): add link to help information
chore(README): add link to help information

Add link to information regarding getting help with Rusoto.
Remove IRC information (it can be found on the help page).

ford-prefect/rusoto,cmsd2/rusoto,DualSpark/rusoto,mthjones/rusoto,DualSpark/rusoto,DualSpark/rust-aws,noggleboggle/rusoto,rusoto/rusoto,mattico/rusoto,mattico/rusoto,DualSpark/rusoto,SecurityInsanity/rusoto,DualSpark/rust-aws,DualSpark/rust-aws,indiv0/rusoto,mthjones/rusoto,rusoto/rusoto,mattico/rusoto,ford-prefect/rusoto,SecurityInsanity/rusoto,rusoto/rusoto