stage_file_proxy 8.x-1.0-alpha3

Changes since 8.x-1.0-alpha2:

• #2751397 by mfernea, NerOcrO, naveenvalecha, aks22, BarisW: Fix coding style to meet Drupal standards
• #2846752 by mfernea, BR0kEN, BarisW: Add an option to skip SSL verification
• #2849596 by volkswagenchick, mark_fullmer, loopduplicate, BarisW: README for 8.x-1.x branch
• #2867108 by roborew: TypeError with webprofiler installed
• #2866908: use_imagecache_root lost
• Factored out variable
• #2820773 by nehakhadke: $this->t() should be used instead of t() for Drupal 8 version
• #2762353 by jalpesh: Drupal 8 Install Instructions
• Fixed log variable
• Fixed phpdoc
• #2795175 by webflo, axel.rutz: Handle guzzle client exceptions gracefully
• Fixed really weird variable name
• #2719737 by NITEMAN: No-hotlink: use cache-control header (avoid redirection loops)
• Simplified code: No need to check origin $server again, amended #2840952
• Fixed broken bracketing for issue #2840952: Hotlink does not redirect to imagestyle path
• Improved comment.
• Removed malign code for #2840952 Hotlink does not redirect to imagestyle path
• #2817761 by mr.baileys, asrob, axel.rutz: Move fixed configuration schema to its correct location
• #2817761 by mr.baileys, asrob, axel.rutz: Fix configuration schema
• Removed now duplicated if (with a lot of indentation change)
• Cleaned up confusing code
• #2819912 by axel.rutz, greggles, asrob: Sleep on production, to prevent endless redirection
• #2464699 by mikeytown2, markdorison, asrob, axel.rutz: Use write & rename instead of write. Also check content length

~/c/stage_file_