Bunch of bug fixes

[plp13]

Hi, I made a these fixes over a year ago, and never pushed them upstream, thinking that the project was dead. Obviously it's not, so I'm submitting them now:

• Bugfix: Black screen upon terminal window resize
• Bugfix: Program crashes when 'man' command fails (e.g. because the requested manual page doesn't exist)
• New feature: Support https URLs
• Bugfix: Pressing 'p' while at the beginning of a man page would crash the program
• Bugfix: Program hangs on startup if the TERM environment variable isn't set
• Bugfix: Program sometimes won't reset the terminal upon abnormal exit

I put comments before the code changes, to make it plain about which is which.