Added "last-known" option

This version adds a "last-known" option.

When given, we will fetch the last known values up to 20 minutes ago. CloudWatch metrics are not always up to date. By specifying this option we will walk back in 1 minute steps when no data is known.

Make DIMENSIONS parameter optional

2.1.12

Fixed $DIMENSIONS parameter being optional

Fixed start/end time which caused NULL values

Merge pull request #31 from level23/empty-values-bugfix

Bugfix attempt for empty returning values

Fixed usage of SECONDS variable which is also an internal bash variable

Merge pull request #30 from level23/seconds-var-fix

Seconds var fix

Bugfix for missing value error

Resolve printf missing value error

Version 2.1.8, added namespace-prefix parameter

This adds support for custom (non-aws) namespaces.

Version 2.1.7, added support for scientific values

This version fixes handling values which are returned from AWS Cloudwatch represented as a scientific value (9.610487596832052e-06). This script converts them now as correct floats.

Version 2.1.6, fixed timeout notice and updated readme with cloudfront example

Merge pull request #22 from level23/timeout-bugfix

Fixed timeout notice on osx, updated readme

Version 2.1.5, fixed incorrect message description

Merge pull request #17 from sherwind/master

make alert messages for OUTSIDE mode consistent with its test condition

Version 2.1.4 Fixed bug in timeout parameter

Merge pull request #16 from level23/timeout_support

bugfix: timeout is /usr/bin/timeout