Add a few tools for C/C++ and Java

- rtags
- irony-mode
- doxymacs
- CMake-Font-Lock
add java/c++ item in TOC
Format issues

1. Add CONTRIBUTING.org for Format guidance(stolen from
https://github.com/fffaraz/awesome-cpp/blob/master/CONTRIBUTING.md).
2. Format most entries accordingly.
3. Put several contribution related items inside CONTRIBUTING.org.
Revert "Format issues"

This reverts commit 00ea27c103acc3acc718751bbb8abf4582af941a.
Merge pull request #32 from HongxuChen/master

Add a few tools for C/C++ and Java
Tidy up the last PR.
Update guideline for contributing.
Tidy up the list.
add ruby relative items
Merge pull request #33 from ripple0328/master

add ruby relative items