Fixed typos and grammar. This fixes reiven/tomber#2

Fixed a few typos and improved the readability of the file. I went
ahead and rephrased a few portions of the file as well, for example, I
rewrote the part that mentioned the pyTomb code, which no longer is
supported.
made minor edits
Merge pull request #3 from JoelMon/typo-fix

Fixed grammar and typos on README.mkdn
Included additional edits to improve readability.

Apart from making minor edits on phrases, additional links were
provided to help the end user find resourced relating to this project.