fixed syntax errors and clarify some grammar
more syntax fixes

Apparently, when I edited this lab earlier I probably did an unfortunate
replace all.
reorganized introduction

changed the introduction to focus more on cython being an automation of
writing a C-extension for Python.
edits to typed declarations section of lab

Reword and reorder some of the content for clarity.
center figures
change python interactive prompt
change interactive prompt symbol

Also removed some legacy labs
change interactive prompt symbol
Merge pull request #263 from ayr0/prompts

Change interactive prompts
Replaced eps files with pdf files for pdflatex compatability on windows.
Merge pull request #264 from insertinterestingnamehere/hotfix

Replaced eps files with pdf files for pdflatex compatability on windows.
Merge pull request #253 from ayr0/cython_fixes

fixed syntax errors and clarify some grammar
Merge branch 'master' into cwrap