add balance Test constructors
added  balance addition unit test
added boost subtraction unit test
add Equality unit test for balance
edited subraction test
add test for multiplication
add unit test for balance division
add unit test negation for balance_t
add unit test Absolute for balance_t
add unit test Ceiling for balance_t
add unit test Floor for balance_t
add unit test Round for balance_t
add unit test Truth for balance_t
add unit test of Zero for balance_t
add unit test printing for balance_t
Revert "add unit test printing for balance_t" until issue is fixed.
Getting different output on system than travis-ci.

This reverts commit 272e3cb3799937dcd3c379de56b299a3cbde52ca.
Merge pull request #316 from tripun/code_coverage

expand unit tests in t_balance.cc