fix minor typos (#2324)

* opening and closing links

* sudo example compiles

* add Aura after it was merged to master

* Timestamp doc testing passes

* Timestamp doc testing works, extraneous lines commented out

* balances

* remove extern crate line

* Removed unneeded code snippet from aura

* make consensus compiles

* executive compiles

* cleanup unnecessary lines

* staking (removed examples that are just copies of tests)

* minor typos

* restore tab spacing