[#3] Support specifying 'anchor' for pattern to alter parse logic.
[#3] Update test to reflect default anchor logic.
[#3] Update default placeholder expression to be non-greedy.

Required to make default logic sensible following introduction of
anchored matches. Without this, the default anchored start match would
result in insufficient portions of a string being consumed.
[#3] Add Template anchor unit tests.
[#3] Fix error caused by unsupported operand against None and int.
[#3] Add ANCHOR_BOTH attribute for ease of use.
[#3] Update guide with information about Template anchor attribute.
Merge pull request #5 from 4degrees/3_support_partial_matching

3 support partial matching