Update README.md

Author: maxgmr

README.md

@@ -1,3 +1,20 @@
 # rcv
 
 An exceedingly simple C program used for quick conversion between radicies.
+
+## Usage
+
+`rcv [OPTION...] [INPUT_NUMBER]`
+
+## Options
+
+* `-b, --bin`: Output as a binary number (radix 2)
+* `-c, --coct-prefix`: Use a C-style octal prefix (leading 0) instead of a Rust-style octal prefix (leading 0o)
+* `-i --dec`: (Default) output as a signed decimal number (radix 10)
+* `-n, --no-newline`: Omit the line feed at the end of the output
+* `-o, --oct`: Output as an octal number (radix 8)
+* `-p, --no-prefix`: Omit the prefix for hexadecimal, octal, and binary output
+* `-u, --dec`: Output as an unsigned decimal number (radix 10)
+* `-x, --hex`: Output as a hexadecimal number (radix 16)
+* `-?, --help`: Display the help page
+* `-V, --version`: Print program version