Documentation fixes

[Edearth]

1. Why?

There are a couple of things wrong in the README, mostly with the receive messages example:

• When connecting the signal, it references print_chatter_msg but the function declared below is named print_chatter_message
• The string in the print is unterminated
• It uses a function called escape_bbcode, which exists in the example project but it might not be straightforward.

2. How?

• Use print_chatter_message in both lines of code.
• Add missing " to the string.
• Remove call to escape_bbcode so the example is more clear.

3. Related Issue

n/a

4. Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules

5. Tests made (if appropriate)

n/a

6. Notes (if appropriate)

n/a

[rothiotome]

Great catch! Thanks!