Merge pull request #1194 from iglesias/develop

Update gitignore and typo fix
OnlineLinearMachine::get_w(): Copy weight before passing them to SGVector to prevent double-free on destruction.
Fix possible memory leak in StructuredOutputMachine
Basic classes
Merge pull request #1186 from van51/feature/hashing

Hashing N-gram / String Converter and tokenizer
Merge pull request #1197 from iglesias/feature/structure_fix_leak

Fix possible memory leak in StructuredOutputMachine
update documentation of gp framework
Merge pull request #1199 from votjakovr/feature/gp_refactoring

update documentation of gp framework
Merge pull request #1196 from tklein23/double_free_hotfix

Fixed double-free when using "SGVector<float32_t> OnlineLinearMachine::get_w()"
Fix json version on travis
Travis: fix cwd before building
refactor likelihood models
Merge pull request #1200 from votjakovr/feature/gp_refactoring

refactor likelihood models
change default value of the derivative wrt hypers
Merge pull request #1201 from votjakovr/feature/gp_refactoring

change default value of the derivative wrt hypers
fixed interactive gp demo, under votjakovr's new GaussianProcessRegression class
Merge pull request #1202 from foulwall/develop

fix graphical interactive gp demo, under votjakovr's new GaussianProcessRegression class
Dot features class for hashing documents
rational approximation using direct solvers added
Merge pull request #1198 from van51/feature/hashing

Dot features class for hashed documents