New chapter for the guide
Use a consistent printing style everywhere
Now byebug plays nice with Rails debugging flag

Regarding issue #2.
Fix a FIXME
Minor changes
Fixes a long-standing bug when printing some lines

Byebug would crash when printing lines of code containing '%' and using
some specific style of calling print. This is now fixed and a regression
test has been added.
Fix bug: basename & linetrace not working together

If you set basename to on, lines of code wouldn't get printed when
tracing enabled.