Updated the building instructions

Instructions from @GonzaGonza:
https://github.com/popcorn-time/popcorn-app/pull/398#issuecomment-37259777
Removed confusing and useless comments
Fix a spelling mistake in README.md
Merge pull request #452 from wdacgrs/patch-1

Fix a spelling mistake in README.md
Merge pull request #440 from 1ace/patch-1

Updated the building instructions
Wipe the tmp folder on close #188. Also removed some stuff from gitignore.
Merge pull request #1 from popcorn-time/master

Last commit from popcorn-time: master