Add installation instructions, including for OpenCV on Windows
Merge pull request #34 from danielballan/install-instructions

Add installation instructions, including for OpenCV on Windows
DOC: minor edits
Merge pull request #35 from danielballan/install-instructions

DOC: minor edits
DOC: More OpenCV instructions edits.
Merge pull request #36 from danielballan/install-instructions

DOC: More OpenCV instructions edits.