Add a method that returns the .text section of any executable file

[postmodern]

Add a method that returns the .text section of any executable file. It should be returned not as a String, as executable files can be quite large, but as some kind of class or IO stream that we can read bytes from. It should also contain information about whether the .text section contains x86, x86-64, ARM, or ARM64/AArach64 object code; this will be useful for selecting the architecture's disassembler from ronin-asm.