Remove calls to impure mathlib functions.
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
Add "Africa/Tripoli" from/to "Libya Standard Time"
Make std.string.indexOf @safe
Mark std.string.indexOf as @safe
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
Mark the constructor of std.string.StringException as nothorw
Merge pull request #1482 from 9rnsr/fix_win_timezone

Add "Africa/Tripoli" from/to "Libya Standard Time"
Merge pull request #1488 from tom-tan/nothrow-string-StringException

Mark the constructor of std.string.StringException as nothorw
Replace trusted lambda block with trusted nested function
Implement pure floor()/ceil().
Implement pure tan().
Implement pure atan().
Implement pure atan2().
Implement pure exp().
Implement pure expm1().