refactor the README to markdown flavore

refinement and refactor of the README file:
(1) rewrite it in Markdown and use Python highlight for the source code
(2) add some information about KGTP to make the document more clear
fix compile time warning when compile for 32-bit kernel
ignore the compiled files, tmp files and other trivial stuff
Merge pull request #25 from hustcalm/master

refactor the README to markdown flavore
Thanks work of Lihang Li <licalmer@gmail.com>.
Merge pull request #27 from lynus/master

fix compile time warning when compile for 32-bit kernel
Merge branch 'master' into dev
Merge pull request #29 from hustcalm/dev

minor fix about the source directory, remove duplication
Update kgtp.pdf according to previous commit.
Update UPDATE
Change ":=" to "?=" in Makefile to let KERNELVERSION, KERNELDIR, CROSS_COMPILE, MODULEDIR and ARCH can be set by "export".
Fix build warning with ARM.
Update URL and year
Add build option "NO_WARNING=1" to let gcc doesn't output warning when build gtp.ko.
Add "Handle the compile errors" to doc.
Add plugin_example temp file to .gitignore
Merge pull request #1 from teawater/dev

Dev
multiple ring buffer allocation for reading memory action whose size is bigger than GTP_RB_DATA_MAX
fix printk warning
Change for_each_online_cpu to for_each_possible_cpu to handle the issue the CPU number issue with Android.
Handle the issue that cannot find GDB in "/usr/local/bin/"

In fedora, "/usr/local/bin/" is not in the PATH when sudo:
sudo python
Python 2.7.5 (default, Jun 25 2014, 10:19:55)
[GCC 4.8.2 20131212 (Red Hat 4.8.2-7)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.environ.get("PATH")
'/sbin:/bin:/usr/sbin:/usr/bin'

Add code to check GDB in "/usr/local/bin/" if PATH doesn't have it.