enforce use of builder to create a new HTTPVaultConnector (#54)

Remove constructors of HTTPVaultConnector and make the builder
constructor package-private to enforce use of .builder()....build()

For convenience we add direct builder constructors with a full URI
argument to allow a one-line initialization if necessary.

README.md

@@ -12,7 +12,7 @@ Java Vault Connector is a connector library for [Vault](https://www.vaultproject
 ## Features:
 
 * HTTP(S) backend connector
-    *  Ability to provide or enforce custom CA certificate
+    * Ability to provide or enforce custom CA certificate
     * Optional initialization from environment variables
 * Authorization methods
     * Token
@@ -40,7 +40,7 @@ Java Vault Connector is a connector library for [Vault](https://www.vaultproject
 <dependency>
     <groupId>de.stklcode.jvault</groupId>
     <artifactId>jvault-connector</artifactId>
-    <version>0.9.4</version>
+    <version>1.0.0-SNAPSHOTf</version>
 </dependency>
 ```
 
@@ -50,21 +50,19 @@ Java Vault Connector is a connector library for [Vault](https://www.vaultproject
 
 ```java
 // Instantiate using builder pattern style factory (TLS enabled by default)
-VaultConnector vault = VaultConnectorBuilder.http()
+VaultConnector vault = HTTPVaultConnector.builder()
  .withHost("127.0.0.1")
  .withPort(8200)
  .withTLS()
  .build();
 
 // Instantiate with custom SSL context
-VaultConnector vault = VaultConnectorBuilder.http()
- .withHost("example.com")
- .withPort(8200)
+VaultConnector vault = HTTPVaultConnector.builder("https://example.com:8200/v1/")
  .withTrustedCA(Paths.get("/path/to/CA.pem"))
  .build();
 
 // Initialization from environment variables 
-VaultConnector vault = VaultConnectorBuilder.http()
+VaultConnector vault = HTTPVaultConnector.builder()
  .fromEnv()
  .build();
 ```