Create new-style issue template (#305)

Author: daviddrysdale

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,23 @@
+---
+name: Bug report
+about: Create a bug report for Python-specific problems
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+Only raise issues that are **specific to the Python version** here, please.
+
+Before reporting an issue with parsing particular numbers, check if the problem also occurs with the online version of the Java code at <https://libphonenumber.appspot.com/>
+
+If the same problem is visible with the Java code, **report the problem upstream** not here:
+
+- [checklist](https://github.com/google/libphonenumber/blob/master/CONTRIBUTING.md#checklist-before-filing-an-issue)
+- (non-GitHub) [issue tracker](http://issuetracker.google.com/issues/new?component=192347).
+
+If the problem **only** occurs with the Python version of the library, continue opening an Issue:
+
+- Delete this template text.
+- Include Python version (`python --version`)
+- Include library version (`python -c "import phonenumbers; print(phonenumbers.__version__)"`)