Generate single html

[EncodePanda]

After this change we get:

1. better UX by providing arguments with flags
2. single html generated from multiple sources
3. templating mechanism (user can provide its own styles)
4. table of contents automatically generated (if $toc$ present somewhere in the template)

Example usage:

• asking for help

  
  $> frost --help                                                                                                         
  Frost - automatically generates documentation from your source code

Usage: frost [--input STRING]... [--template STRING] --output STRING

Available options: -h,--help Show this help text --input STRING... Files from which documentation is generated. Accepts multiple values --template STRING (optional) HTML template used to generate the documentation --output STRING Path to a file that will hold generated documentation

* creating documenation with template (that has table of content in it)

$> frost --input ./examples/git.md \ --input ./examples/python.md \ --output doc.html --template ./examples/standalone.html

gives us

![image](https://user-images.githubusercontent.com/6287558/75578248-c74a0300-5a63-11ea-9eb7-82e24630633e.png)

[lukasz-golebiewski]

Cool stuff! Travis is unhappy though

[EncodePanda]

@lukasz-golebiewski Travis is now happy :)

[EncodePanda]

Template from https://github.com/diversen/pandoc-uikit