Make versionsLT support versions with qualifier (#307)

Extracted functions to jenkins-support; included in both jenkins.sh and
install-plugin.sh.

Added a separate test file to test versionLT function
diff --git a/tests/functions.bats b/tests/functions.bats
new file mode 100644
index 0000000..6745b10
--- /dev/null
+++ b/tests/functions.bats
@@ -0,0 +1,24 @@
+#!/usr/bin/env bats
+
+load 'test_helper/bats-support/load'
+load 'test_helper/bats-assert/load'
+load test_helpers
+
+. $BATS_TEST_DIRNAME/../jenkins-support
+
+@test "versionLT" {
+  run versionLT 1.0 1.0
+  assert_failure
+  run versionLT 1.0 1.1
+  assert_success
+  run versionLT 1.1 1.0
+  assert_failure
+  run versionLT 1.0-beta-1 1.0
+  assert_success
+  run versionLT 1.0 1.0-beta-1
+  assert_failure
+  run versionLT 1.0-alpha-1 1.0-beta-1
+  assert_success
+  run versionLT 1.0-beta-1 1.0-alpha-1
+  assert_failure
+}