Test with PostgreSQL too (#309)

* Test with PostgreSQL too

* Add 'test' to Travis build stages

* Add test coverage for postgresql

script/compute_coverage.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+wget https://github.com/SimonKagstrom/kcov/archive/master.tar.gz &&
+tar xzf master.tar.gz &&
+mkdir -p kcov-master/build &&
+cd kcov-master/build &&
+cmake .. &&
+make &&
+sudo make install &&
+cd ../.. &&
+for file in target/debug/*-*[^\.d]; do
+	if [[ -x "$file" ]]
+	then
+		filename=$(basename $file)
+		mkdir -p "target/cov/$filename"
+		kcov --exclude-pattern=/.cargo,/usr/lib --verify "target/cov/$filename" "$file"
+	fi
+done &&
+bash <(curl -s https://codecov.io/bash) &&
+echo "Uploaded code coverage"