Merge pull request #1 from kennethreitz/master

Pulling in the latest changes.
Clarified point about variable names

"Avoid using variables for different things" is misleading at best. The
point must communicate that foolish reuse of _the same_ variable name,
for different types of data, is the hobgoblin of reckless minds :)
Merge pull request #242 from lambdadi/master

Clarified point about variable names, under Dynamic Typing