[Bioc-devel] shrunken vignette

Hi all,
My package 'maftools' finally found its homepage today. But when I checked the vignette, it has been shrunken. It appears to be html vignette is center aligned rather than left aligned. It makes things cluttered and and toc looks messy. 
Vignette is here: http://bioconductor.org/packages/devel/bioc/vignettes/maftools/inst/doc/maftools.html
When I build it manually on my computer with devtools::build_vignettes() it looks like this. http://poisonalien.github.io   - A much cleaner look.
Do I need to change any thing in markdown file?
Meta data on my vignette markdown looks like this.
---title: "maftools : Summarize, Analyze and Visualize MAF files"author: "Anand Mayakonda"date: "`r Sys.Date()`"output: BiocStyle::html_document2vignette: >  %\VignetteIndexEntry{Summarize, Analyze and Visualize MAF files}  %\VignetteEngine{knitr::rmarkdown}  %\VignetteEncoding{UTF-8}---

Thank you.