Fix range check for string versions

Fixes #267

Author: michaelwoodson

jruby-gradle-base-plugin/src/main/groovy/com/github/jrubygradle/internal/GemVersion.groovy

@@ -169,8 +169,8 @@ class GemVersion {
             return 1
         }
 
-        int aaObject
-        int bbObject
+        def aaObject
+        def bbObject
 
         if (aDigits[index].isInteger() && bDigits[index].isInteger()) {
             // compare them as number

jruby-gradle-base-plugin/src/test/groovy/com/github/jrubygradle/internal/GemVersionSpec.groovy

@@ -178,4 +178,28 @@ class GemVersionSpec extends Specification {
         expect:
         subject.intersect('[1.2.4, 1.2.4]').conflict() == true
     }
+
+    def "passes non-integer version ranges with no conflicts"() {
+        given:
+        GemVersion subject = new GemVersion('[1.2.bar, 1.2.foo]')
+
+        expect:
+        !subject.conflict()
+    }
+
+    def "fails non-integer version ranges with conflicts"() {
+        given:
+        GemVersion subject = new GemVersion('[1.2.foo, 1.2.bar]')
+
+        expect:
+        subject.conflict()
+    }
+
+    def "it does not throw an exception for a '+' version"() {
+        when:
+        new GemVersion('+').conflict()
+
+        then:
+        notThrown(Exception)
+    }
 }