use explicit template include loader

see issue #6.
build tests with unsafePerformIO
use total functions with explicit handler

see issue #7
use pure loadTemplate function
add non-working infrastructure
use tagless final parser
use builder
fix typo that is rejected by ghc 7.8
support array-like indexing for variables
adjust api and bump version to use it
resolve includes in final style
rename to stencil
make me maintainer