Make it possible to add options to the compiler.

Just set somewhere (~/.vimrc, local .vimrc with
https://github.com/MarcWeber/vim-addon-local-vimrc, or somewhere else)
variable g:typescript_compiler_options to include all additional optinos
for tsc compiler.
Merge pull request #31 from mcepl/compiler_options

Make it possible to add options to the compiler.