doc(automatic_builds): add how to prevent a build on Travis-ci

[skip ci]
fix(debug): print type in lean_assert, print bool correctly

 - use typeinfo to print out a type of value when an assertion fails.
   need to use "c++filt --types" to demangle names for non-basic types.
 - use std::boolalpha and std::noboolalpha to control the printed values
   for "true" and "false"
chore(travis): use c++filt to handle demangled c++ names
test(util/numerics/mpbq): add more tests for improving coverage