Fix README spelling errors and inconsistency

[FireIsGood]

The README had a few spelling errors and inconsistencies to the capitalization. They were mostly split into a few categories of fixes:

• Capitalization inconsistencies (Name was capitalized differently)
  • Spelled with capitals on the main link (mitmproxy -> Mitmproxy)
  • Other random words (linux -> Linux)
• Minor spelling errors
  • Andriod -> Android

yay