Date-time string parsing improvements

• Add more support for parsing date-time strings using different LDML patterns (see LDML formats)
  • Era
  • Quarters and stand-alone quarters
  • Month names and stand-alone month names
  • Day periods (am/pm/noon/midnight)
  • More hour formats (1-12, 0-11, 1-24)
  • More second formats
  • More fractional second formats
  • More time zone formats
• Documented more LDML caveats
• Era names can now be customized

LDML fixes & documentation

• Fix for issue #35: AM/PM not parsed and formatted correctly
• Fix for formatting of O and OOOO patterns which used 'UTC' instead of 'GMT'
• Fix for formatting of ZZZZZ patterns which did not use 'Z' when appropriate
• Allow setting locale in DateTime#parse()
• Documented the LDML formats that we do and do not support
• Changed copyright from Spirit IT to ABB because company has been acquired by ABB

DateTime#format() no longer throws

• updated all (dev)dependencies
• ensure that DateTime#format doesn't throw
• improve code coverage
• test against newer Node.JS versions

v5.4.4: more argument checks in DateTime constructor

v5.4.4

v5.4.3: fix incompatibility with typescript 2.0

v5.4.3

v5.4.2: upgrade typescript to 2.1.4, strict null checks

v5.4.2

v5.4.1: bugfixes in Duration#equalsExact() and Period#equals().

v5.4.1: bugfixes in Duration#equalsExact() and Period#equals().

v5.4.0: add tzdata as a dependency

v5.4.0: add tzdata as a dependency.

Make it easier to get the standard offset without DST

v5.3.0

v5.3.0

v5.2.0: add Duration#divide() method that takes another Duration and outputs a unitless number.

build