Change Log:
v0.4.1 - bug fixes
  - fixed problem in delete spell function that would give errors on some deactivate.vertices calls
  - fixed bug in get.vertex.activity(as.spellList=TRUE) when spell activity had been deleted or removed
  - fixed bug in get.change.times that prevented it from checking changes times of TEAs
v0.4 - new functionality and bug fixes
  - networkDynamic() function supports conversion from various tabular schemas (spell-edgelists, toggles, lists of networks)
  - added ability to attach Temporally Extended Attributes (TEAs) to network elements to store and manipulate changing attributes of vertices, edges and networks.
  - specification of an (optional) net.obs.period attribute to store meta-information about the network's period of observation/simulation
  - added network.collapse() function (and %k% operator) which complements network.extract() for extracting an appropriate static network from a dynamicNetwork object
  - added support for networks with zero vertices (feature added in network)
  - addition of as.network.networkDynamic and as.networkDynamic.network to remove and set networkDynamic class on network objects. 
  - added package dependency on statnet.commons for startup message functionality
  - added package suggests to testthat to support more efficient writing of unit tests. 
  - extensive and updated package vignette / tutorial: browseVignettes(package='networkDynamic')
  - numerous bug fixes and documentation improvements

v0.3 - bug fixes and new functionality
	- network.dynamic.check now optionally reports what is wrong with an element
	- new functions get.vertex.activity and get.edge.activity to return activity matrices of elements
	- new function get.change.times to report timepoints at which network structure changes
	- new convienince function add.edges.active and add.vertices.active which add and activate elements in a single call
	- new delete.edge.activity and delete.vertex.activity functions to remove timing information from elements. 
	- activate.* and deactivate.* methods now modify class of network argument in place. 
	- speed and stability improvements to many functions
	- additional examples in help files
	- dactivate.vertices function now includes option to deactivate incident edges

v0.1-0 - Lots of rebuilding
 - added namespaces
 - moved duration.matrix script from ergm code, added some C code
 - update to package loading
 - renamed network.crossection to network.extract
 - ndConverter functions for translating various forms of relational information into networkDynamic format
 - addition of 'at' and 'length' arguments for most temporal methods
 - rebuilt code with increased argument checking for most spell related methods
 - added test cases for most methods
 - some changes in spec for spell handling
 - bug fixes in spell handling for interval queries
 - bug fix to network.dynamic.check
 - added dynamic network datasets of Newcomb's fraternities, Lin Freeman's Windsurfers and McFarland's classroom networks
 - filename of build now includes version information

v0.1-1 - Internal Bugfix Release, w/Minor New Function
  New Functions:
    - network.dynamic.check: Check dynamic consistency of network elements.
  Bug Fixes:
    - Removed tracer statements.  [Submitted by PNK]
    - is.active could fail if passed no edges to check.  [Submitted by PNK]
    - is.active could fail if passed infinite arguments in some cases.

v0.1 - Initial Internal Release