Update README.md

Add nightly build for 'pu' branch
Do not try to free SSL connection on error

This fixes core dumps that occur occasionally when using an unstable
connection. See issue #47 for details.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Makefile: Do not strip library by default

This allows for using the standard mechanisms for creating debug
packages provided by a lot of package managers. Almost all package
managers invoke strip(1) after the make process anyway, so removing it
won't hurt. You can still invoke `make strip` to strip the dynamic
library when compiling manually.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
README.md: Minor wording and formatting changes

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Makefile: Add debug target

This allows for easily creating a library with debug symbols by running
`make debug`.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
README.md: Add note on including debug symbols

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Free cipher contexts

This is targeted at removing the major source of memory leaks described
in issue #13.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>