Add rubocop lint checking rake task

not added to default target yet, as currently failing
Fix Rspec expect() usage errors

We have discovered that when using the following syntax:

    expect(thing) == thing_value

... that Rspec silently works, though the assertation is not actually
operational -- the '.to' is missing.

Hence, `expect(false) == true` passes!

Fixed up all cases to use the correct syntax using eq() and other matchers.
Fix logic error in vApp#power_on test

Whilst fixing up the expect syntax errors in 85e2639, this test
started to fail.

The test logic was wrong -- returning :status => 8 each
time would emulate a machine NOT powering on.

Updating the test to return 8 (STOPPED), then 4 (RUNNING)
fixes the behaviour emulation, and hence the test now passes.
Use rspec matchers rather than '=='

Highlighted by Rubocop as 'Operator == used in void context' errors, but
it is recommended to use rspec matchers rather than the == operator.

In the process, update to the Rspec 3.0 expect syntax.
Remove unused 'obj' variable

Highlighted by Rubocop as "Useless assignment to variable obj"
Account for unused arguments in StubFogInterface

(fixing Rubocop warnings)
Remove unused block argument in Rakefile

(fixing Rubocop warnings)
Remove trailing whitespace
Remove assignments in conditionals

These are generally considered a bad smell, since they look
like conditionals but are not.

Highlighted by rubocop lint checker.
Remove useless private access modifier

(fixes Rubocop error)

Class methods are not affected by the 'private' modifier, so it
not actually doing anything in this case.
Avoid rescuing Exception class

(fixes Rubocop warning)

Catching Exception is dangerous, since it includes exceptions that are not
errors.

This instead rescues StandardError, which is safe and what we actually require here.

See http://www.mikeperham.com/2012/03/03/the-perils-of-rescue-exception/ for more detail.
Fix "interpreted as grouped expression" warning

Rubocop lint highlights that before (:each) is ambiguous, that
the (:each) could be considered a grouped expression like (1 + 1)

Removing the space between the method (before) and the argument
parenthesis removes this ambiguity, and hence the warning.
Remove redundant vapp_name var

The vapp_name variable was set here so that it would be available
in the underlying ERB template.

The Vm#vapp_name method covers this though, as confirmed with the updated tests.
Merge pull request #41 from alphagov/70437918_rubocop_and_fixes

[#70437918] rubocop lint checking, and related fixes