Update to v0.1.2 with HTML support

moved posterdown_pdf to posterdown_latex, added posterdown_html, added to ReadME, added ciation file. added @shedimus  as contributor in Description file.
diff --git a/inst/rmarkdown/templates/posterdown_latex/template.yaml b/inst/rmarkdown/templates/posterdown_latex/template.yaml
new file mode 100644
index 0000000..b5d418f
--- /dev/null
+++ b/inst/rmarkdown/templates/posterdown_latex/template.yaml
@@ -0,0 +1,4 @@
+name: Posterdown LaTeX
+description: >
+ Template for creating R Markdown based PDF via LaTeX
+create_dir: true