Mathops extensions

Add a new `math_rpn` function, and capacity to add new operators when using the RPN parser.
New operators (RPN only): `exp`, `floor`
Built README
Corrected typos.
Rebuilt README
Fixed bugs with processing m4 in fedora init scripts
Merge pull request #158 from nikbyte/master

Fixed bugs with processing m4 in fedora init scripts
Correct an error message
Merge pull request #144 from shimaore/mathops_extension

Mathops extension: new RPN expression parsing function