Fix past participle tense in docs (dmlc#2637)

Author: eculver

doc/R-package/index.md

@@ -4,7 +4,7 @@ XGBoost R Package
 [![CRAN Downloads](http://cranlogs.r-pkg.org/badges/xgboost)](http://cran.rstudio.com/web/packages/xgboost/index.html)
 
 
-You have find XGBoost R Package!
+You have found the XGBoost R Package!
 
 Get Started
 -----------

doc/jvm/index.md

@@ -3,7 +3,7 @@ XGBoost JVM Package
 [![Build Status](https://travis-ci.org/dmlc/xgboost.svg?branch=master)](https://travis-ci.org/dmlc/xgboost)
 [![GitHub license](http://dmlc.github.io/img/apache2.svg)](../LICENSE)
 
-You have find XGBoost JVM Package!
+You have found the XGBoost JVM Package!
 
 Installation
 ------------