Add README

A must for good Github repos
Add Contribution Guidelines

Github will "add a link to your file when a contributor creates
an Issue or opens a Pull Request".
https://github.com/blog/1184-contributing-guidelines
do reverse of a bytecode in lookbehinds
backtracking matcher works with reversed bytecode
ditto with Thompson matcher
cleanup to keep lookahead/lookbehind more in sync for future

Fix 64 bit issues, remove useless debug hook
Made unix domain sockets work on Linux.
Made the fix apply to all unices and added a unit test.
fix broken indention, detab
Add proper docs for return type of sformat.
Merge pull request #1503 from AndrejMitrovic/DocFix

[Trivial] Add proper docs for return type of sformat.
Fix issue 10874.

Don't assume that is(A : B) means a==b is valid, or that !is(A : B)
implies that a==b is invalid. Instead, test for a==b explicitly.

More specifically, int and ulong are ==-comparable, even though ulong is
not implicitly convertible to int. Thus, one should be able to convert
ulong to an int-based enum, but is(A : B) in the signature constraint
prohibits this. Testing for a==b explicitly, OTOH, makes this work.
Fix frexp for real == double targets
Merge pull request #1506 from jpf91/frexp

Fix std.math.frexp for real == double targets
Add unittest for issue 6893.
Allow narrowing conversions of enum -> integral (int, short, etc.).

It will just throw at runtime if the value of the enum is too large.
Add unittest for narrowing enum -> integral conversions.
Mark std.string.stripRight as @safe and pure
Mark std.string.strip and its unittests as @safe and pure
Mark std.string.chompPrefix and its unittests as @safe and pure