Fix Javadoc warnings in SerpApi, SerpApiHttp, and ParameterStringBuilder

Author: jvmvik

src/main/java/serpapi/ParameterStringBuilder.java

@@ -10,6 +10,12 @@
  */
 public class ParameterStringBuilder
  {
+   /**
+    * Default constructor
+    */
+    public ParameterStringBuilder() {
+    }
+
    /***
     * getParamsString 
     * @param params search parameters

src/main/java/serpapi/SerpApi.java

@@ -131,6 +131,8 @@ private JsonObject json(String endpoint, Map<String, String> parameter) throws S
   }
 
   /***
+   * Get the HTTP client used for requests
+   * 
    * @return http client
    */
   public SerpApiHttp getClient() {

src/main/java/serpapi/SerpApiHttp.java

@@ -189,27 +189,35 @@ protected void triggerSerpApiException(String content) throws SerpApiException {
   }
 
   /**
+    * Get the HTTP connection timeout
+    * 
     * @return current HTTP connection timeout
     */
   public int getHttpConnectionTimeout() {
     return httpConnectionTimeout;
   }
 
   /**
+   * Set the HTTP connection timeout
+   * 
    * @param httpConnectionTimeout set HTTP connection timeout
    */
   public void setHttpConnectionTimeout(int httpConnectionTimeout) {
     this.httpConnectionTimeout = httpConnectionTimeout;
   }
 
   /**
+   * Get the HTTP read timeout
+   * 
    * @return current HTTP read timeout
    */
   public int getHttpReadTimeout() {
     return httpReadTimeout;
   }
 
   /**
+   * Set the HTTP read timeout
+   * 
    * @param httpReadTimeout set HTTP read timeout
    */
   public void setHttpReadTimeout(int httpReadTimeout) {