Fix EOF detection

Fixes issue with Ctrl-D having to be pressed twice when reading from
terminal.
Merge pull request #232 from nwellnhof/eof_detection

Fix EOF detection
Revised README's instructions on tests.
Added note on lua wrapper.
Update benchmarks.md

Fixed a typo. Prenalized should be penalized.
Create pkg-config file as part of build procedure.

Closes #234.
Merge pull request #235 from coder543/patch-1

Update benchmarks.md
Fixed some problems in 'make archive'.
Fixed another archive problem.
Moved source files from src/html into src.

The separate directory presents problems for some simple
extension building systems, like luarocks.
Added "chunk.h" include to scanners.h.
Added CMARK_NODE_TYPE_NONE.

This is the return value of cmark_get_node_type when the argument
is a null pointer.  Avoids segfault.
Changed CMARK_NODE_NONE from -1 to 0.

This is more consistent with CMARK_LIST_NONE, etc.
node.c:  Make sure no functions segfault if passed null pointers.
API change:  Add cmark_node_set_type for completeness.
Revert "API change:  Add cmark_node_set_type for completeness."

This reverts commit 6c1f76a8a22f6c84231e5101f0950ce353ec8075.