Markdown support

[rudychung]

Fixes #4

I added:

• support for reading .md files, both from an input directory and input file
• reading bold markdown indicators
• reading italic markdown indicators

I attempted to change as little of the original source code as possible. I used regex to search for the markdown indicators and index slicing to remove the indicators that were replaced by HTML tags. There is some code repetition that needs to be resolved on the function that I added to convert markdown indicators to the appropriate HTML tags.

[sfrunza13]

Thank you for adding MD support, could you also add support for multiple MD elements in the same new line?