string: add assign methods

tests: change function name to match behaviour

add vector range() and crange() methods

Run tests on tmpfs on travis

fix string's methods description

Improve code coverage for locking APIs and transactions.

test: add gnome-terminal support

string: add compare functions

Limit test execution time on AppVeyor.

test: rm vector_private test

vector: add comparison operators between pmem::vector and std::vector

add .gitattributes

Merge back changes from stable-1.5

extend vector API

set text and eol config parameteres

explicitly cast values to match parameters

travis: run valgrind tests only in one configuration.

and run tests with valgrind only in one configuration on travis.

add comparison operators between vector and std::vector

Explicit cast is required for persistent_ptr (array type overload)
operator[] which now takes integral_type, but after merge back
from stable 1.5 will require std::ptrdiff type.

test: port miscellaneous libcxx's vector tests

Change it in vector ctors and assign method.