Add help text to signup form

- first pass on verbage
- 🙏 thanks to crispy forms this is stupid easy

Closes #68
5 jobs for 68-signup-help in 2 minutes and 52 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #2729
Go-py2.7

00:01:32

passed #2730
Go-py3.4

00:01:39

passed #2731
Go-py3.5

00:01:35

passed #2732
Go-py3.6

00:01:36

 
  Lint
passed #2733
Go-flake8

00:01:13