Add LGTM.com configuration file (#337)

The YAML configuration file for the LGTM static analysis tool can be
either lgtm.yml or .lgtm.yml:
	https://lgtm.com/help/lgtm/lgtm.yml-configuration-file

There is no need to integrate the LGTM tool in CI, as LGTM appears to
be running on all repositories it has been run on once. The results
currently appear here:
	https://lgtm.com/projects/g/zarr-developers/numcodecs

Exclude vendored file cpuinfo.py from analysis.

Author: DimitriPapadopoulos

.lgtm.yml

@@ -0,0 +1,17 @@
+---
+# This file contains configuration for the LGTM tool: https://lgtm.com/
+# The numcodecs repository is continuously scanned by the LGTM tool for
+# any security and/or code vulnerabilities. You can find the alerts here:
+# https://lgtm.com/projects/g/zarr-developers/numcodecs
+
+extraction:
+  python:
+    index:
+      exclude: cpuinfo.py
+
+path_classifiers:
+  test:
+    - numcodecs/tests
+
+queries:
+  - exclude: py/clear-text-logging-sensitive-data

docs/release.rst

@@ -24,6 +24,9 @@ Maintenance
 * Remove trailing spaces and empty lines.
   By :user:`Dimitri Papadopoulos Orfanos <DimitriPapadopoulos>`, :issue:`341`.
 
+* Add LGTM.com configuration file
+  By :user:`Dimitri Papadopoulos Orfanos <DimitriPapadopoulos>`, :issue:`337`.
+
 .. _release_0.10.0:
 
 0.10.0