[SPARK-12910] Fixes : R version for installing sparkR

Testing code:
```
$ ./install-dev.sh
USING R_HOME = /usr/bin
ERROR: this R is version 2.15.1, package 'SparkR' requires R >= 3.0
```

Using the new argument:
```
$ ./install-dev.sh /content/username/SOFTWARE/R-3.2.3
USING R_HOME = /content/username/SOFTWARE/R-3.2.3/bin
* installing *source* package ‘SparkR’ ...
** R
** inst
** preparing package for lazy loading
Creating a new generic function for ‘colnames’ in package ‘SparkR’
Creating a new generic function for ‘colnames<-’ in package ‘SparkR’
Creating a new generic function for ‘cov’ in package ‘SparkR’
Creating a new generic function for ‘na.omit’ in package ‘SparkR’
Creating a new generic function for ‘filter’ in package ‘SparkR’
Creating a new generic function for ‘intersect’ in package ‘SparkR’
Creating a new generic function for ‘sample’ in package ‘SparkR’
Creating a new generic function for ‘transform’ in package ‘SparkR’
Creating a new generic function for ‘subset’ in package ‘SparkR’
Creating a new generic function for ‘summary’ in package ‘SparkR’
Creating a new generic function for ‘lag’ in package ‘SparkR’
Creating a new generic function for ‘rank’ in package ‘SparkR’
Creating a new generic function for ‘sd’ in package ‘SparkR’
Creating a new generic function for ‘var’ in package ‘SparkR’
Creating a new generic function for ‘predict’ in package ‘SparkR’
Creating a new generic function for ‘rbind’ in package ‘SparkR’
Creating a generic function for ‘lapply’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘Filter’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘alias’ from package ‘stats’ in package ‘SparkR’
Creating a generic function for ‘substr’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘%in%’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘mean’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘unique’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘nrow’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘ncol’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘head’ from package ‘utils’ in package ‘SparkR’
Creating a generic function for ‘factorial’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘atan2’ from package ‘base’ in package ‘SparkR’
Creating a generic function for ‘ifelse’ from package ‘base’ in package ‘SparkR’
** help
No man pages found in package  ‘SparkR’
*** installing help indices
** building package indices
** testing if installed package can be loaded
* DONE (SparkR)

```

Author: Shubhanshu Mishra <smishra8@illinois.edu>

Closes #10836 from napsternxg/master.

1 files changed, 10 insertions, 0 deletions

diff --git a/R/README.md b/R/README.md
index 005f56da16..bb3464ba99 100644
--- a/R/README.md
+++ b/R/README.md
@@ -1,6 +1,16 @@
 # R on Spark
 
 SparkR is an R package that provides a light-weight frontend to use Spark from R.
+### Installing sparkR
+
+Libraries of sparkR need to be created in `$SPARK_HOME/R/lib`. This can be done by running the script `$SPARK_HOME/R/install-dev.sh`.
+By default the above script uses the system wide installation of R. However, this can be changed to any user installed location of R by setting the environment variable `R_HOME` the full path of the base directory where R is installed, before running install-dev.sh script.
+Example: 
+```
+# where /home/username/R is where R is installed and /home/username/R/bin contains the files R and RScript
+export R_HOME=/home/username/R
+./install-dev.sh
+```
 
 ### SparkR development