Add coverage of TinkerPop 3.6.x and 3.7.x

[krlawrence]

As a rider to issue #115 , this issue is to track adding specific examples relative to the TinkerPop 3.6.0 release.

There needs to be a new section in the introduction chapter and then detailed coverage of each feature.

The new coverage needs to include

• Changes to by to act more like filters
• New mergeV and mergeE
• A new TextP.regex predicate and the inverse TextP.notRegex
• The property step can now take a map
• New fail step
• New call step
• New element step

Specific to 3.7.x

• New concat() step
• union is now a start step
• mergeV cardinality support
• TinkerGraph transactions
• Properties on elements (vs reference elements)
• Mid traversal E() is now supported

[krlawrence]

This work will now be done as part of the Second Edition. As such, each of the key items listed at the top of this issue should be broken out into issues of their own.

[krlawrence]

Closing this one. Will still use #115 for tracking the overall work still to be done. Individual issues will be opened for large pieces of work that need doing.