Server#responsive? now rescues all SystemCallError exceptions

It previously only rescued Errno::ECONNREFUSED and Errno::EBADF. On a
few occasions, I have also seen the Errno::ETIMEDOUT exception raised by
Net::HTTP from this method. Since the Net::HTTP calls are the only thing
in this method that should be making any kind of system calls, a rescue
of all SystemCallError exceptions (the superclass of all of the Errno
exceptions) will catch these as well as any other system call errors
triggered by Net::HTTP.
Removes specs not directly related to the patch
Delay requiring selenium until driver is used, closes #1018
Fix xpath in base versions gemfile
Revert "Delay requiring selenium until driver is used, closes #1018"

This reverts commit 07f2a714acd67b278451e5fef0de2d915ae8b994.
Delay loading selenium until driver in instantiated

Another attempt at fixing #1018
Merge pull request #1015 from jwilger/responsive_rescues_system_call_error

Server#responsive? now rescues all SystemCallError exceptions
Mention requirement of Ruby 1.9.3
typo
Remove documentation about `match` option

The documentation isn't correct anymore, since matching on symbols
like this is no longer allowed. `match` is such an obscure option
that it does not need to be mentioned in the README anyway.
Merge remote branch 'jnicklas/master' into capybara-2.1
Remove timeout divergences.