Dubov Pavel, Calculator

Answers to some questions are in comments. Should I add unit-tests? How
deep should we think about OOP?
Minor improvements

Added toUpperCase, stricter lexem analyzer.
Changed BigFractions to overflow-safe Integers. Improved style. Separated classes.
Files relocation. Package headers added.
Internal class constants access modifiers have been restricted.
Lexem numeration is started from 1 now. Answer is written in the given radix. Exit statuses added. Whitespace-containing numbers are not lon
Код коллеги Ивановского.
For fuck's sake. ><
Unary minus is now supported.
Minor logic improvement.
Merge pull request #30 from dubov94/master

Dubov Pavel, 296, Calculator, initial