get.php: Add query GET variables

Issue #146.
lib: Add a Pip_Query class

This class provides a representation of a query.

Issue #146.
Merge branch 'release/0.1.7'
tools/pipbot: Fix invalid var ref

Issue #193.
tools/pipbot: Print newline after summary

Issue #193.
tools/pipbot: Push changes before deleting

Issue #193.
tools/pipbot: Push to stable

Issue #193.
tools: Delete workflow script

Functionality is now implemented in pipbot:

    pipbot start  <issue|feature|release>
    pipbot pause  [issue|feature|release]
    pipbot finish [issue|feature|release]
        Start, pause or complete work on an upstream issue,
        downstream feature, or product release branch.

Issue #194.
Merge branch 'issue/194'
configure.ac: Don't check for git flow

Issue #203.
build/tools: Remove HAVE_GIT_FLOW check

Issue #203.
README: Remove gitflow from dependency list

Issue #203.
scripts: Remove git flow files

Issue #203.
Merge branch 'issue/203'
tools/pipbot: Support short time deltas

If we have a time delta that is less than an hour ago, we weren't
returning anything for the time string.
Example:

    $ pipbot burndown release
    Comparing 'master' against 'stable'...

      There are 5 new commits
      Last commit was  ago

This adds support for short time spans (less than one hour).
Example:

    $ pipbot burndown release
    Comparing 'master' against 'stable'...

      There are 5 new commits
      Last commit was 27 minutes ago
tools/pipbot: Always print the last commit time

Even though we may not have made a commit, it's still useful to know
when the last commit was.
tools/pipbot: Don't print '0 minutes'

For time deltas of less than a minute, this means that only the seconds
are printed, instead '0 minutes, X seconds'.
Example:

   $ pipbot burndown
   Comparing 'HEAD' against 'master'...

      There are no new commits
      Last commit was 0 minutes, 7 seconds ago
tools/pipbot: Correctly pluralise single units

Example: "1 minute" vs "1 minutes"
tools/pipbot: Show last release version in burndown

This transforms:

    $ pipbot burndown release
    Comparing 'master' against 'stable'...

      There are 9 new commits
      Last commit was 47 minutes ago

Into:

    $ pipbot burndown release
    Comparing 'master' against 'stable'...

      The last release was 0.1.7
      There are 9 new commits
      Last commit was 47 minutes ago
tools/pipbot: Show branch names on burndown

This transforms:

    $ pipbot burndown release
    Comparing 'master' against 'stable'...

      The last release was 0.1.7
      There are 9 new commits
      Last commit was 47 minutes ago

Into:

    $ pipbot burndown release
    Comparing 'master' against 'stable'...

      The last release was 0.1.7
      There are 9 new commits on master
      Last commit on stable was 47 minutes ago