First release of 0.8 series

New rules

• bank() (#188 by @malkusch - only german support)
• bankAccount() (#188 by @malkusch - only german support)
• bic() (#188 by @malkusch - only german support)
• false() (#263 by @henriquemoody)
• filterVar() (#267 by @henriquemoody)
• true() (#263 by @henriquemoody)
• type() (#280 by @henriquemoody)
• url() (#269 by @henriquemoody)

Updated rules

• max() (#292 by @henriquemoody): better support for date and time comparison
• min() (#292 by @henriquemoody): better support for date and time comparison
• when() (#247 by @henriquemoody): allow to use rule without else's constraint

Other changes

• #176: Allow to define custom rule's namespaces/prefixes (by @henriquemoody)
• #261: Remove dead code on AbstractRule (by @henriquemoody)
• #265: Performance optimization in NumberPrime.php (by @camilotx)
• #272: Now using Respect\Validation exceptions only (by @AndyWendt)
• #279: Update contributing guidelines (by @henriquemoody)
• #288: Optimize PrimeNumber rule (by @l-x)
• #289: Make Roman rule internally use Regex rule (by @l-x)
• #290: Remove allow failures on HHVM builds (by @henriquemoody)