send_file accept full and relative paths, not require file to be in public_dir
add test for send_file full path outside base tree
template type control/support

* compiles templates according to type (index.html.erb is :html type)
* `erb` renders template by type prioritizing:
    * `:type` option given (ex: `erb :index, type: :xml`)
    * 'Accept' request header value
    * 'Content-Type' response header value
    * defaults to :html
update changelog and readme
update readme
typo
mustermann now requires >= ruby-2.1
add 2.1.5 to travis
slight fix for warnings, update changelog