Update issue templates (#903)

* Update issue templates

* Rename general-questions.md to general_questions.md

.github/ISSUE_TEMPLATE/bug_report.md

+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+Thanks for your bug report and we appreciate that a lot.
+
+**Checklist**
+- [ ] I have searched related issues but could not get the expected help.
+- [ ] The bug has not been fixed in the latest version.
+
+**Describe the bug**
+A clear and concise description of what the bug is.
+If there are any related issues or upstream bugs, please also refer to them.
+
+**Error traceback**
+1. What command or script did you run?
+```
+A placeholder for the command.
+```
+2. If applicable, paste the error trackback here using code blocks.
+```
+A placeholder for trackback.
+```
+
+**Reproduction details**
+1. Did you make any modifications on the code? Did you understand what you have modified?
+2. What dataset did you use?
+
+**Environment**
+ - OS: [e.g., Ubuntu 16.04.6]
+ - GCC [e.g., 5.4.0]
+ - PyTorch version [e.g., 1.1.0]
+- How you installed PyTorch [e.g., pip, conda, source]
+- GPU model [e.g., 1080Ti, V100]
+- CUDA and CUDNN version
+- [optional] Other information that may be related (such as `$PATH`, `$LD_LIBRARY_PATH`, `$PYTHONPATH`, etc.)
+
+**Bug fix**
+If you have already identified the reason, you can provide the information here. If you are willing to create a PR to fix it, please also leave a comment here and that would be much appreciated!

.github/ISSUE_TEMPLATE/feature_request.md

+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Describe the feature**
+
+**Motivation**
+A clear and concise description of the motivation of the feature.
+Ex1. It is inconvenient when [....].
+Ex2. There is a recent paper [....], which is very helpful for [....].
+
+**Related resources**
+If there is an official code release or third-party implementations, please also provide the information here, which would be very helpful.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.
+If you would like to implement the feature and create a PR, please leave a comment here and that would be much appreciated.

.github/ISSUE_TEMPLATE/general_questions.md

+---
+name: General questions
+about: Ask general questions to get help
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+