add docs (#75)

NEWS.md

+TVM Change Log
+==============
+
+This file records the changes in TVM library in reverse chronological order.
+
+## Initial version (0.1rc)
+   - CUDA/OpenCL codegen
+   - LLVM codegen
+   - AOT and module system
+   - External function call
+   - Beta verilog codegen

docs/how_to/contribute.md

+# Contribute to TVM
+
+TVM has been developed and used by a group of active community members.
+Everyone is more than welcome to contribute. It is a way to make the project better and more accessible to more users.
+
+- Please update [NEWS.md](../NEWS.md) to add note on your changes to the API or added a new document.
+
+## Guidelines
+* [Submit Pull Request](#submit-pull-request)
+* [Git Workflow Howtos](#git-workflow-howtos)
+  - [How to resolve conflict with master](#how-to-resolve-conflict-with-master)
+  - [How to combine multiple commits into one](#how-to-combine-multiple-commits-into-one)
+  - [What is the consequence of force push](#what-is-the-consequence-of-force-push)
+* [Document](#document)
+* [Testcases](#testcases)
+* [Examples](#examples)
+* [Core Library](#core-library)
+* [Python Package](#python-package)
+
+## Submit Pull Request
+* Before submit, please rebase your code on the most recent version of master, you can do it by
+```bash
+git remote add upstream [url to tvm repo]
+git fetch upstream
+git rebase upstream/master
+```
+* If you have multiple small commits,
+  it might be good to merge them together(use git rebase then squash) into more meaningful groups.
+* Send the pull request!
+  - Fix the problems reported by automatic checks
+  - If you are contributing a new module, consider add a testcase in [tests](../tests)
+
+## Git Workflow Howtos
+### How to resolve conflict with master
+- First rebase to most recent master
+```bash
+# The first two steps can be skipped after you do it once.
+git remote add upstream [url to tvm repo]
+git fetch upstream
+git rebase upstream/master
+```
+- The git may show some conflicts it cannot merge, say ```conflicted.py```.
+  - Manually modify the file to resolve the conflict.
+  - After you resolved the conflict, mark it as resolved by
+```bash
+git add conflicted.py
+```
+- Then you can continue rebase by
+```bash
+git rebase --continue
+```
+- Finally push to your fork, you may need to force push here.
+```bash
+git push --force
+```
+
+### How to combine multiple commits into one
+Sometimes we want to combine multiple commits, especially when later commits are only fixes to previous ones,
+to create a PR with set of meaningful commits. You can do it by following steps.
+- Before doing so, configure the default editor of git if you haven't done so before.
+```bash
+git config core.editor the-editor-you-like
+```
+- Assume we want to merge last 3 commits, type the following commands
+```bash
+git rebase -i HEAD~3
+```
+- It will pop up an text editor. Set the first commit as ```pick```, and change later ones to ```squash```.
+- After you saved the file, it will pop up another text editor to ask you modify the combined commit message.
+- Push the changes to your fork, you need to force push.
+```bash
+git push --force
+```
+
+### Reset to the most recent master
+You can always use git reset to reset your version to the most recent master.
+Note that all your ***local changes will get lost***.
+So only do it when you do not have local changes or when your pull request just get merged.
+```bash
+git reset --hard [hash tag of master]
+git push --force
+```
+
+### What is the consequence of force push
+The previous two tips requires force push, this is because we altered the path of the commits.
+It is fine to force push to your own fork, as long as the commits changed are only yours.
+
+## Testcases
+- All the testcases are in [tests](../tests)
+- We use python nose for python test cases.
+
+## C++ Library
+- Follow Google C style for C++.
+- We use doxygen to document all the interface code.
+- You can reproduce the linter checks by typing ```make lint```
+
+## Python Package
+- Always add docstring to the new functions in numpydoc format.
+- You can reproduce the linter checks by typing ```make lint```

verilog/README.md

+# Verilog Code Guidline
+
+- Use ```my_port_name``` for variable naming.
+- Always use suffix to indicate certain usage.
+
+## Common Suffix
+
+- ```clk```: clock
+- ```rst```: reset
+- ```in```: input port
+- ```out```: output port
+- ```en```: enable signal
+- ```addr```: address port
+- ```valid```: valid signal in FIFO handshake.
+- ```ready```: ready signal in FIFO handshake.