Don't encode ':' or '/' as part of the canonical representation

This makes the Java canonical representation match the majority of
other implementations.

Fixes package-url#122
Fixes package-url#92

Author: dwalluck

src/main/java/com/github/packageurl/PackageURL.java

@@ -460,7 +460,7 @@ private static String uriEncode(String source, Charset charset) {
     }
 
     private static boolean isUnreserved(int c) {
-        return (isAlpha(c) || isDigit(c) || '-' == c || '.' == c || '_' == c || '~' == c);
+        return (isAlpha(c) || isDigit(c) || '-' == c || '.' == c || '_' == c || '~' == c || ':' == c || '/' == c);
     }
 
     private static boolean isAlpha(int c) {

src/test/resources/test-suite-data.json

@@ -86,7 +86,7 @@
   {
     "description": "docker uses qualifiers and hash image id as versions",
     "purl": "pkg:docker/customer/dockerimage@sha256:244fd47e07d1004f0aed9c?repository_url=gcr.io",
-    "canonical_purl": "pkg:docker/customer/dockerimage@sha256%3A244fd47e07d1004f0aed9c?repository_url=gcr.io",
+    "canonical_purl": "pkg:docker/customer/dockerimage@sha256:244fd47e07d1004f0aed9c?repository_url=gcr.io",
     "type": "docker",
     "namespace": "customer",
     "name": "dockerimage",
@@ -110,7 +110,7 @@
   {
     "description": "maven often uses qualifiers",
     "purl": "pkg:Maven/org.apache.xmlgraphics/[email protected]?repositorY_url=repo.spring.io/release&classifier=sources",
-    "canonical_purl": "pkg:maven/org.apache.xmlgraphics/[email protected]?classifier=sources&repository_url=repo.spring.io%2Frelease",
+    "canonical_purl": "pkg:maven/org.apache.xmlgraphics/[email protected]?classifier=sources&repository_url=repo.spring.io/release",
     "type": "maven",
     "namespace": "org.apache.xmlgraphics",
     "name": "batik-anim",
@@ -122,7 +122,7 @@
   {
     "description": "maven pom reference",
     "purl": "pkg:Maven/org.apache.xmlgraphics/[email protected]?repositorY_url=repo.spring.io/release&extension=pom",
-    "canonical_purl": "pkg:maven/org.apache.xmlgraphics/[email protected]?extension=pom&repository_url=repo.spring.io%2Frelease",
+    "canonical_purl": "pkg:maven/org.apache.xmlgraphics/[email protected]?extension=pom&repository_url=repo.spring.io/release",
     "type": "maven",
     "namespace": "org.apache.xmlgraphics",
     "name": "batik-anim",