OpenQuake Hazardlib 0.18.0

[Daniele Viganò (@daniviga), Matteo Nastasi (@nastasi-oq)]

• Updates Copyrights to 2016 and uniformize them

[Michele Simionato (@micheles)]

• SiteCollection instances are now serializable in HDF5 format

[Graeme Weatherill (@g-weatherill)]

• Adds `arbitrary' magnitude frequency distribution
• Adds version of NSHMP Western US (NGA West) GMPEs to calculated the
  weighted mean of the epistemic uncertainty adjustment factor

[Nick Ackerley (@nackerley)]

• Implemented GMPE of Kanno et al. (2006) for shallow and deep earthquakes.
• Implemented GMPE of Raghukanth & Iyengar (2007) for stable continental
  regions of peninsular India.
• Implemented GMPE of Nath (2012) for anomalous interface subduction in the
  intraplate margin of the Shillong plateau in India.
• Implemented GMPE of Gupta (2010) for Indo-Burmese intraslab subduction.
• Implemented GMPE of Sharma et al. (2009) for active shallow crust of
  Indian Himalayas.
• Give more feedback in error messages on validation.

[Michele Simionato (@micheles)]

• Added a .weight property to sources, as well as a .num_ruptures attribute
• The GMPETable now understands paths relative to a directory GMPE_DIR

[Graeme Weatherill (@g-weatherill)]

• Implements Drouet (2015) GMPE for Brazil
• Revises Montalva et al. (2015) GMPE (on author's advice)

[Silvia Canessa (@silviacanessa)]

• Adds Dowrick and Rhoades 2005 GMPE

[Michele Simionato (@micheles)]

• Fixed the equality check for SiteCollections: now all of the parameters
  are compared, not only lons and lats.

[Yen-Shin Chen (@vup1120)]

• Modified the hypocentre_patch_index method to obtain the best solution