Added README explaining how to use.

README.md

@@ -0,0 +1,60 @@
+# Flexible-CAP
+
+Flexible-CAP is a flexible Commandline Argument Parser.
+
+Using a custom argument specification language, it will generate a corresponding lexer and parser in Flex and Bison respectively.
+
+This can then be compiled with the other source files to generate a program using the commandline interface specified.
+
+# Requirements
+
+* `flex`
+* `bison`
+* [`mstch`](https://github.com/no1msd/mstch)
+* `g++`
+
+# Compiling
+
+First build the generator.
+
+If you have `tup` installed:
+
+```sh
+tup init
+tup
+```
+
+If you do not, on Linux:
+
+```sh
+./build.sh
+```
+
+# Usage
+
+Once the generator has been built, write an `ArgSpec` file specifying the interface of your program.
+
+Then, produce the interface files with:
+
+```sh
+/path/to/cloned/repo/generator/fcap /path/to/argument-specification.argspec
+```
+
+This will produce the required files in the directory the command is run from.
+
+There should be 6 files produced:
+
+```sh
+${argspec}ArgGrammarDriver.cpp
+${argspec}ArgGrammarDriver.hpp
+${argspec}ArgGrammarParser.yy
+${argspec}ArgGrammarScanner.cpp
+${argspec}ArgGrammarScanner.hpp
+${argspec}ArgGrammarScanner.ll
+```
+
+Here, the `${argspec}` denotes the name of the `.argspec` file without the extension.
+
+Next, run `bison` on the `${argspec}ArgGrammarParser.yy` file, and run `flex` on the `${argspec}ArgGrammarParser.yy`.
+
+Then, compile and link all the `.cc` and `.cpp` files together with your application.