Documentation for build in Linux environment

[deepujain]

Update Readme with pre-requisite steps for building in Linux environment.

[minduni]

Here the steps to build the nvidiagpubeat binary on a RedHat ES 7.3:

• Software requirements installation

yum install python-virtualenv
yum install golang

• Actual build of the executable

cd ~   
mkdir beats_dev 
export WORKSPACE=`pwd`/beats_dev
export GOPATH=$WORKSPACE
git clone https://github.com/elastic/beats ${GOPATH}/src/github.com/elastic/beats --branch 6.5
mkdir $WORKSPACE/src/github.com/deepujain
cd $WORKSPACE/src/github.com/deepujain
git clone https://github.com/deepujain/nvidiagpubeat
cd nvidiagpubeat/
make copy-vendor
make

[deepujain]

@minduni Thanks for the steps. eBay repository no longer uses "deepujain".

Could you please give a PR for README.md . Also, clearly indicate that the executable was indeed built after the steps ( ls -l )

[deepujain]

Updated.