Add Firefox support

The release.bash script has been updated, and now depends on a helper
script called generateManifest.bash. A "--browser" flag (shorthand "-b")
has been added to the script in order to specify the target browser.

Now the manifest.json file is saved as a template at
templates/manifest.gjson (gjson stands for Generic JSON), which includes
conditional clauses which indicate what parts of the manifest are
applicable to each browser.

generateManifest.bash generates the src/manifest.json file.

Change-Id: Ib051f3d893045c1377007b9b076ffa7a702d9648
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..a2fb83e
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,18 @@
+.PHONY: all chromium-stable chromium-beta gecko-stable gecko-beta clean
+all: chromium-stable chromium-beta gecko-stable gecko-beta
+	bash release.bash -c stable -b chromium
+	bash release.bash -c beta -b chromium
+	bash release.bash -c stable -b gecko
+	bash release.bash -c beta -b gecko
+	rm -rf out