Omit decimal points for integers and refactor

Details

• Modify add_spaces_to_triples to omit decimal point for integers
• Correct Examples section in uc --help output
• Upgrade C standard, enhance compiler warnings, and improve documentation

Insert previous result into expression using Tab key

Details

• Add function to handle Tab key press and insert previous result

It seems to work fine.

Details

• Support of readline library(.inputrc)
• Support of raise a number to a power
• -h, --help, -v, --version

It seems to work.

Details

Essential functions of the program are now implemented.