doc(ubuntu-*): add 'python-software-properties' in the required packages

It's for 'add-apt-repository'.
doc(ubuntu-*): remove eglibc warning

We're using filib++ to evaluate elementary functions, instead of using
the ones in C math library (such as EGLIBC).
feat(util/scoped_vec): add get_vec method
refactor(dsolvers/icp_solver): remove m_explanation
feat(dsolvers/icp_solver): add get_explanation method
feat(dsolvers/nra_solver): add m_explanation_stack
feat(realpaver/rp_constraint): mark used only if ctr is unfeasible
fix(CMakeLists.txt): rename CAPD to CAPD3
tests(capd3): add tests
fix(util/scoped_vec): add missing "std::"
feat(opensmt,dsolvers): use unordered_map if possible
fix(util/hexfloat): fix style
refactor(dsolver/ode_solver): clean up
feat(CMakeLists.txt): add 'util' and 'tests' in style check
refactor(dsolvers/ode_solver): clean up step control
feat(realpaver): make rp_expression_eval, rp_erep_eval const
feat(realpaver): implement rp_box_equal
feat(realpaver/rp_operator_sat): mark ctr c used if box is improved
refactor(dsolver/nra_solver): add debug message for the size of explanation
chore(travis): respect branch name when push to bitbucket and osx repo