Added colon and space before user input

[michalbundyra]

I think it is much nicer to have : in the question for user input. Now we have:

$ keep-a-changelog config -g
Please select the provider (Default: github)
  [0] github
  [1] gitlab
 > 0
Please enter the personal token for the provider (Empty to skip)f4my-private-token-super-secret0
Please enter the custom domain for the provider, if any (Empty to skip)
Created config file "/home/.keep-a-changelog/config.ini".

and with the change we have:

$ keep-a-changelog config -g
Please select the provider (Default: github)
  [0] github
  [1] gitlab
 > 0
Please enter the personal token for the provider (Empty to skip): f4my-private-token-super-secret0
Please enter the custom domain for the provider, if any (Empty to skip): 
Created config file "/home/.keep-a-changelog/config.ini".

[weierophinney]

Thanks, @webimpress!