WIP: exceptions

Helpers: microoptimized isInt()

updated website URL

README: included example.php & improved instructions

added Printer

Solver: solution is returned for initial objective function variables

Solver: only one alternative solution is calculated

Solver: added solutions as class properties

added Solver::getSolutionValue()

Solver: separated initial solving steps & table steps

fraction values set as strings

Table: key value stored in a variable (microoptimization)

Fraction: create() is immutable

Helpers: improved gcd() - used loop instead of recursion

added Math as a wrapper for bcmath functions