Grabbit

This is a major, backwards-incompatible release that changes the `Layout`initialization API. Changes include:
* Major refactoring of the way Domains are handled and indexed. From a user standpoint, the main change is to the Layout initialization arguments; see Layout docstring for details (69).
* Minor domain-related bug fixes (66, 67).

This release includes a major refactoring of the internal code, but maintains backward compatibility in the user-facing API. Changes include:
* Elimination of the concept of a static root folder for each Domain in favor of a scan-time search path (63)
* Allow querying with `None` values for to-be-ignored keys (thanks to effigies; 62)
* Fix filtering bug (59)
* Prevent keyword names that conflict with reserved keywords from breaking queries (60)

This release adds several improvements and fixes:
* Introduces "Domains", which allow mapping multiple configs to multiple directories (49)
* Refactored file writing functionality (41, 42)
* Adds coveralls support (54)
* Adds ability to parse entities in filenames without updating Layout index (52)
* Adds ability to specify Entity dtypes (52)
* Simplified/revised config file fields (54)
* New global file-filtering arguments (include and exclude; 54)
* Various minor bug fixes and improvements (43, 44, 48)

This release adds several new features. In the interest of making the .PATCH version number meaningful, it also bumps the version to 0.1.0. New features:
- Enables flexible file path construction and writing (thanks to qmac)
- Adds a Layout merging utility and enables initialization of a compound Layout created by passing in multiple project roots
- Allows lists to be passed to any argument when matching files (e.g. via .get())

This release adds several new features:
- Experimental support for HDFS (thanks to ValHayot)
- Ability to include or exclude certain directories from indexing (thanks to adelavega)
- Refactored code to support more modular extensions to other file systems
- Ability to write indexes out to, and reconstruct from, static .json files
- Support for arbitrary entity mapping functions passed by name in the config file

Minor improvements and bug fixes:
- Adds option to use strict matching when calling get_nearest()
- Adds ability to exclude certain directories from indexing (thanks to adelavega)
- Fix travis config