Update tutorial.md

corrected spelling of Fahrenheit and Celsius
Merge pull request #70 from maloneyl/patch-2

Update tutorial.md
Add zero-width spaces to enable emphasis to work

The bolding of the letters HTTP in HyperText Transfer Protocol are not quite working as expected due to the way that the asterisks are being interpreted mid-word. Adding in some zero-width spaces enables the asterisks to be interpreted as expected.
Merge pull request #71 from zoodor/patch-4

Add zero-width spaces to enable emphasis to work
Merge pull request #72 from codebar/master

merge master to gh-pages