build: Add yml file for appveyor.

This is the most simple scenario as we only build 32bit libraries in the
debug configuration. This commit also adds the AppVeyor badge to
README.md.

Signed-off-by: Philip Tricca <philip.b.tricca@intel.com>
diff --git a/.appveyor.yml b/.appveyor.yml
new file mode 100644
index 0000000..939d118
--- /dev/null
+++ b/.appveyor.yml
@@ -0,0 +1,13 @@
+version: '{build}'
+pull_requests:
+  do_not_increment_build_number: true
+skip_tags: true
+image: Visual Studio 2017
+configuration:
+  - Debug
+platform:
+  - x86
+build:
+  project: tpm2-tss.sln
+  parallel: true
+  verbosity: normal