Add a template for reporting issues, including advice on log files

Closes #88

issue_template.md

@@ -0,0 +1,35 @@
+# Instructions
+
+_If reporting a bug, please fill in the template below.  This instructional section should be deleted before submitting the issue._
+
+## Log files
+
+**Please do not include log files with issue reports.  Log files are _very_helpful, and sometimes essential for tracking down and fixing bugs in the software.  However, they may contain personal information including the phone numbers of users interacting with the gateway, or contents of the SMS messages that the gateway has sent and received.**
+
+## Device details
+
+For each device, please fill in a column of the **Device(s) tested** table.
+
+-----
+
+# Device(s) tested
+
+key | value(s)
+---|---
+medic-gateway version | _e.g. 0.1.2_
+device make | _e.g. Nokia_
+device model | _e.g. 5110_
+can the problem be recreated on this device? | _yes or no_
+
+# Observed behaviour
+
+_When I..., then..._
+
+# Expected behaviour
+
+_I would expect..._
+
+# Steps to recreate
+
+1. ...
+2. etc.