Reviewed devtools.md

Note that I added some details about the limitations of the simulator.
I also added stuff about why using alert is bad.
Fixed typos
Reviewed devtools.md

Note that I added some details about the limitations of the simulator.
I also added stuff about why using alert is bad.
Fixed typos
Merge branch 'devtools' of https://github.com/marcoscaceres/firefoxos-quick-guide into devtools
Merge pull request #17 from marcoscaceres/devtools

Devtools