IMPORTANT: This release reverts a change from 2.18.0

In the previous release (2.18), we prematurely merged a partial change to the crypto functions that led to creating two sets of crypto functions (I blame @technosophos -- since that's me). This release rolls back that change, and does what was originally intended: It alters the existing crypto functions to use secure random.

We debated whether this classifies as a change worthy of major revision, but given the proximity to the last release, we have decided that treating 2.18 as a faulty release is the correct course of action. We apologize for any inconvenience.

Changes

• Fix substr panic 35fb796e3ed3869e2df7be0e4fcb5e8b2c425453 (Alexey igrychev)
• Remove extra period 1eb7729022202c016475c4f4d0cb2c463c22c5fe (Matthew Lorimor)
• Make random string functions use crypto by default 6ceff26ca2586bda18e788afef093b7d89e70023 (Matthew Lorimor)
• README edits/fixes/suggestions 08fe136717db5c06a7dd9ee140f9de7070774c78 (Lauri Apple)