crypto: basic crypto functions
crypto - second draft, including suggested changes
crypto: basic crypto functions
crypto - thrid draft
Docstring and test cleanup for the crypto module
Merge pull request #1 from asmeurer/joyner_crypto

Your patch from https://github.com/sympy/sympy/pull/1854/files#r3310621
Merge remote-tracking branch 'github/crypto' into crypto
Docstring and test and html cleanup for the crypto module
Implemented Morse encoding and decoding
Restricting enciphering only to alphabets and digits
Merge pull request #2 from ankit-maverick/crypto

Implemented Morse code and Restricted enciphering only to alphabets and digits
Minor refactoring
Merge pull request #3 from ankit-maverick/crypto

Minor refactoring
Improve subs for Derivative.

Perform substitutions if derivative variables are in a different, but
equivalent order and perform substitutions for subderivatives.
Added slow tests to the travis system.
Timeout the slow tests in Travis to less than 10 minutes
Seconds, not minutes
Run the slow tests in Travis with a timeout of 5 minutes
Fix the failing finite_rv slow tests
Add additional tests for Derivative subs method.